I think prior to that game in Madrid last season I was always in the keep Keita camp. Simply because if he did only play 25-30 odd games in all competitions then there was nothing wrong with that, especially given he generally had a positive impact when he did get on the pitch. He was shocking that night though, don't think he played again last season after that and ended up on 16 appearances overall. I think we'll be looking to move him on.
Personally I'd keep Chamberlain. I think there's a good reason we didn't see much of him even when he was fit last season. Given the state of the defence, there was no room for him in midfield because we needed players there who'd offer the defence a bit more protection. Unless we were chasing a game, he'd always come on for one of the front three. He does frustrate at times but if he can chip in with the sort of tally he did in 19/20 then he's worth keeping around. He's versatile too. We may see more of him in the front three next season, especially if you sell Origi and Shaqiri. No reason why Chamberlain can't have Origi's minutes if he stays fit. I wouldn't be against him filling in for TAA if needed either. Technically I think he has the attributes to do that but it would be going the other way that might be a worry.
No idea on Wijnaldum's replacement. Got to bring someone in though. You can't let a player who played about 50 games a season leave without replacing them.