There are many things I'm hoping, but one essential thing that EVERYONE seems to agree on is this:
Add post-game content that allows you to interact with key characters such as Triss, Yennifer, Ciri, etc. This interaction could be in the form of short and long quests and romances, etc. Leaving Geralt stranded alone in Kaer Morhen caused many players to feel depressed and empty, so CD Projekt Red should definitely fix this. CDPR could even throw in a plot cliffhanger, leaving room for a Witcher 4 game or another Witcher game.
ONCE THOSE ESSENTIAL IDEAS ARE IMPLEMENTED IN THE EXPANSION, then obviously we expect the normal things and features that should come with an expansion. These two expansions will apparently be the size of Witcher 2, which is fantastic news.
I have faith that CDPR actively reads these forums and some of our ideas may even be used in the expansion. They haven't disappointed us yet. They've done the opposite, and they've blown us away with this perfect game that will set the bar for RPS games in decades to come. They started with a small budget, and finished with a big game, revolutionising RPS games, transforming the very genre as we know it. Witcher 3 is a masterpiece, and these expansions will definitely perfect it even more.