As someone who read Last Wish and Blood of Elves, played both games and even enjoyed the atrocity that was the TV serie, I hope I can tell both Yen and Triss to sod off in Witcher 3, because I feel it would make most sense with everything that has happened in previous games (with Geralt reoccurring from death, loosing his memory, boinking Triss etc.) as well as previous lore that Geralt would be a bit cautious to who he will end up with.
Initial thoughts
I mentioned this on my initial account but I'll say it again now, CD RED haven't dealt with romance particularly well.... Or rather it was done fine, but too little and too far between, and both games follow a similar role. Give you a nice piece in the start, then nothing until somewhere in the middle, again nothing and finally the conclusion.
Essentially it feels like CD RED best and worst characteristics is that they are such fans of the books, because this means they have designed a game where you "should know" how much these people mean to you because they as developers already know this. The problem is that if the gamer is solely "being told" instead of actually "getting to experience" the romance it's way harder to actually care for the romantic options.
It's weird to say but it's seems that there is a conflict of interest in how the game was designed. Geralt is a witcher, a loner and because he doesn't have companions, you as the player are merely told on how important these characters are rather than actually getting to experience itself (because all romance is pushed aside for the importance of the story etc.). In contrast the strength of Dragon Age, Pillars of Eternity etc. is that these games gives you, the player the option to interact with people you find interesting/likeable which delivers a far more stronger impact.
As of such both previous games have felt like a lazy written TV serie where the only people who really know how much Triss/Shani/Yen should mean to the player are the developer themselves (because you can't justify a game from the books. The game should hold water regardless of the books).
Here's a broad summary on the romance in previous games.
This contains minor spoilers from previous games, viewer discretion is advised!
Romance in Witcher 1
Well it started well, you have a conversation in Kaer Morhen with Triss which was meaningful, then a hug and then bye bye! You meet again in Act III, watching Triss having a conversation with another sorceress on how she's been hiding things from Geralt and will continue to do so. You can't press her for further details expect asking who she talked with and that's that.
Now to the bizarre part. You base your relationship on whom you'll give Alvin to... But giving Alvin has nothing to do with Geralt's romantic choice, but rather who is better for Alvin. Give him to Shani and you are giving him a more "normal" life, where he will grow up together with other children with a "normal" parent. Give him to Triss if you believe his magical powers are dangerous and he need to be able to control them.
This isn't who Geralt trust more (it's even said so by his dialogue right after the decision) or care more for. It's his decision in a dangerous situation on who would be the better parent for Alvin... Also Geralt isn't the father figure here yet, Alvin has also been tossed around prior to this to both Abigail, the Reverend and left at St. Lebioda's hospital. Alvin is nothing more than a magical orphan and Geralt's interest is solely that he is in safe hands nothing more (at least still to this point).
After this you then have again a meaningful moment where you, Dandelion and Zoltan discuss the possibility of Geralt having a family... And then you are separated again for Murky Waters. You run around there a bit, write a letter to your loved/friend on your feelings, have a brief conversation with Foltest and the game end.
Romance in Witcher 2
This game... ooh this game... You start in the bed with Triss, have a brief conversation, to then run after Foltest. Act I, you go to Flotsam, where you and Triss do your own things for most of the act until you express "pleasantry" in the elven bath and talk whether you should follow Roach or just ignore it all and go after Yen. You are then separated for the entire game, finds out in the end that she might have lied and deceived you and you can either save her or help Roach/Iorveth.
The funny part is that because we never see much romance or deep conversations with Triss it causes people to not even save her in the last act... Something everyone would do in an instant if it was your friend/loved one. Sure some of it got spoiled because people "knew" she would be saved either way, but this isn't true for the first playthrough and the very notion that a person that should mean a lot for you essentially is thrown aside for all be it, important issues is so easily done, do highlight some design issues by CD RED.
Some good things has been showed however with Witcher 3. It does seem that you can invest more heavily on the relationship/romance role, but I really hope that there's much more emphasis on actually interactions/dialogues between Geralt and his loved ones. Not only quest related conversations but actually just things in general, so that you as the player get to know (especially if you're new to the franchise) what sort of people you have around you.
Now to something a bit different.
People I want to romance in Witcher 3
There's a couple of people that I find far more interesting than Yen & Triss (treating this game franchise individually and not based upon books).
Abigail
Seriously CD RED, stop being a wanker and bring her back! She's awesome and fit Geralt extremely well!
- She's a witch, which means she is an outcast that is hated but still necessary for humans just as Geralt
- She's powerful and can help Geralt in dangerous situations
- She knows shit tonne of Lore, monsters, history, prophesies & alchemy
- She is used to wandering and probably around Geralt's vicinity, since she probably left Murky Water once Nilfgaard got there (because Nilfgaard doesn't treat "ramping" sorceresses particularly well courtesy of Letho) so she will fit well with Geralt monsterslaying.
- She's a Lionhead Spider Cultist (Awesome!), which means you can have awesome discussions with her of all sort of things that Geralt won't already know
- She's similar as witcher's as she doesn't care if people end up using her services for evil, as long as she get paid.
Abba
Literally every conversation you had with her in Witcher 1 was stellar and hilarious. It also was perfectly crafted, because it told the player on what sort of character both she and Geralt was. It would be problematic for Geralt to "date" her, but because of her previous involvement with Geralt it could be justified as Geralt "watching over her". She's also powerful (which is good for Geralt) but despised (because of the curse) which again summarizes Geralt pretty well. Because we are also now in Novigrad (Radovid's realm) it would make sense to meet her.
Morenn
I actually liked her from the TV-serie (shucks huh?!) and think she would bring a nice dynamic to Geralt. She's caring for the living and could help Geralt if he ever get wounded, but on the same time would be willing to follow him wandering around. She's a dryad which again could give people interesting lore and also the combination between not being liked by most humans but still caring for Geralt would be a nice contrast. As all dryad she's also good with the bow and could help Geralt at range if the wilderness ever would be too problematic for him. Same as Abba, she would be in the area (Brokilon is close) so you could make a reason to meet her again.