MMO in Witcher World! ASAP!!! PLEASE! ^^ Creating our own characters (not only witchers ofc) and all races. That would be just epic!
"The Witcher 3: Wild Hunt is the final Witcher game with Geralt of Rivia at center stage". This is apparent also from how the story of the game is written. Not sure if making a sequel only for monetary reasons to a story that does not really need one is a good idea, but CDPR may eventually end up doing it, who knows.
They can't possibly make a continuation, because Geralt dies in one of the endings.
He is not actually shown dying, so it could still be explained in a hypothetical sequel.
It doesn't really matter if he's dead phisycally. He should be a walking zombie either way in this ending. He failed to save Ciri. He'd never recover after this.
Ciri's death is not confirmed either, she could still come back. And if the sequel takes place some longer time after the ending of TW3 (say, 5-10 years), then it can be explained why none of Geralt's choices matter by that time, and (for example) Ciri is always a witcher (or empress ?), Geralt is alone, Skellige is not in the game and does not matter, and the political situation in the North and Nilfgaard always ends up being the same after so long time.
You can't have a 007 movie without James Bond and you can't have a Witcher game without Geralt of Rivia.
Anyway, I'm of the opinion that you need to know where to stop. And CDPR knows it as well. Time to move on