City is appealing to the CAS. CAS is generally pretty spineless, so I'd imagine the two year ban will be reduced to one. Depending on when the appeal is heard, City may still be able to play CL next year, but then be banned for 2021-2022.
CL 2020/21 starts with preliminary rounds in June of this year, so I don't know if UEFA needs to decide on all teams in the tournament at that time or, since the Prem has their teams go straight to the group stage, if those teams can be swapped out later.
Personally, if City are going to be banned, it would be great if it were for the upcoming campaign - imagine if Sheffield United were in the group stages of CL!
This ban has potential to really damage City, however - especially if the two year ban is upheld. Players at their peak, like De Bruyne, will want to play CL and likely want to leave. Pep is unlikely to extend his contract again, and there are rumours that he may end up at Juventus.
The next couple months will be quite interesting.