Here is a german interview with Philip Weber, questdesigner at CDP:
http://www.gamersglobal.de/interview/witcher-3-blood-and-wine?page=0,0
There isn't really anything new or specific but it's still a great interview with some interesting bits.
- With Blood&Wine being the last adventure for Geralt and having a longer development than Hearts of Stone, they wanted to "pull everything off"(dunno how to translate "alles raushauen" correctly). Whenever they had a creative or crazy idea, they planned to do it.
- Some things will have influence on other regions. For instance, you may meet someone from Toussaint in Novigrad.
- Some decisions from the main game will have influence on Blood&Wine
Asked about if Geralt will be able to romance Anna Henriette, he points to the books.There are reasons why he may or may not have a romance with her. (sounds rather like it won't be the case) Though he also says "Geralt remains Geralt", so I dunno.
- we will meet some characters from the main game.
Asked about if one of those characters is Dandelion, he answered with "maybe".
- He speaks a bit about the general atmosphere (much more humorous than the main game) and about the housing ( a few small buffs/ no big impact on the gameplay but important if you want to experience everything that the story has to offer)
Mentions guests visiting Geralt
- They got a lot of more experience with the engine, which allows them to make Toussaint look better without sacrificing performance
-Asked if people might miss the more "dark" atmosphere of the base game, he says that Blood&Wine is what act 4 was in Witcher 1. He mentions that they have a few things in store for Witcher 1 fans. "Witcher 1 fans will recognize many little things in Blood&Wine"
Asked about Iorveth he basically explains his absence with the Scoia'tael being a big part of Witcher 1&2 and them wanting to do something different this time.
Iorveth was a part of the game and he saw his quest. At some point it was decided to cut him out. Thy asked themselves if he meets their quality requirements (well, apaprently he didn't) They could have let him stay in the game because many fans would have wanted that, but decided to not do that.
- Speaks again about Witcher 1 (he is a huge fan of the first game) and that a certain sword will make a comeback in Blood&Wine. Apparently he wanted the sword to be in the expansion and wrote a little quest about it. It's a funny quest for people who only played Wild Hunt and a great moment for people who played Witcher 1.