OK, I had this wild tangent of ideas how some of the earlier mentioned discrepancies in the timeline might actually work.
I think that most of it, if not all might actually be by design on CDPR's part.
If true it makes for one hell of a complicated storyline, where certain paradoxes are part of the overall story, but it will also give us nice layer of depth.
Here goes,
So it all started in the distant past with the Elven sages. (Aen Saevherne)
These Elven sages were known for their incredible knowledge of the world, but also their incredible magical powers.
The sages were working on a long term plan to create a pure bloodline known as Hen Ichaer (Elder Blood).
The purpose of the elven sages for Hen Ichaer was to create an individual with powers exceeding even their own. This individual was to safe Elven kind from total annihilation, and bring the race as a whole closer to a divine existence.
Two races of elves are known to exist at the time of the Witcher games.
The Aen Elle and the Aen Seidhe. What I do not know for sure is whether these two races actually have the same ancestral origins, but I presume they do.
The Aen Elle appear to live in another realm, and still are a ruling civilization there. The the Aen Seidhe came to the northern lands in their white ships and settled the lands of the North, building a beautiful civilization which fell into decline over a longer period of time.
The Aen Sheide were also driven from their lands by the humans later on, who actually build their own cities and villages on the remnants of the Elven settlements.
In the nothern lands the Elves became a divided race, not strong enough to resist Humanity's ever gaining power, and also losing connection to their ancestral knowledge of the world.
One of the greatest losses the Elves had to deal with in their history, was losing the Elder Blood and it's remarkable properties.
Lara Doren who was of Elven Elder Blood fell in love the human mage Cregannan of Lod, and their daughter Riannon was adopted by Queen Cerro of Redania.
It was because of this that Riannon basically grew up as human royalty.
Riannon later married king Goidemar of Temeria which meant that the Elder Bloodline now no longer was part of the Elven race, but was inherited by Humans instead.
The genes of Lara Doren apparently provide the carriers of elder blood a great aptitude in magical arts, as well as the gift to bend/manipulate time and space.
It is known that the Aen Elle consider the elvish loss of the Elder Blood to be one of the worst disgraces to be ever in existence.
Since we now know that the Wild Hunt in fact are a band of Aen Elle cavalry riders who are basically terrorizing Humanity, and also seem to be able to manipulate time and space, things might actually start to become more clear.
What if these riders are actually on a crusade to reclaim the Elder Blood and in the process use their time bending powers to reset certain parts of history ?
Might it be that Geralt escaped the riders in an alternate timeline, where historical events actually played out differently ?
Might there actually be multiple timelines where things have altered slightly ?
Was Alvin also captured by the Wild Hunt and placed in a different time period ?