I keep hearing this other CDPR rpg that isn't a Witcher game. I'm not sure I've seen any proof of that. I do know they mentioned they'd like to continue the franchise and explore someone other than Geralt.
I look forward to what InXile has cooking as well.
It is mentioned (and subsequently covered in some online stories) in CDPR's corporate filings: two big RPGs to be released between 2017 and 2021. the first we know is Cyberpunk. The second, CDPR has commented it is not a Witcher game and that's all they will say about it.