I know it's not a perfect like for like comparison, but Chelsea was subject to the transfer ban in summer 2019 while its appeal was pending. I just did some quick research and it looks like a stay is possible but not automatic. You have to make a motion to have the sanction stayed while the appeal is pending. I would expect Man City is likely to be successful in getting a stay, but it's not a given. To add another imperfect data point, Caster Semenya appealed a negative decision by the CAS to the Swiss Supreme Court, which first stayed the ruling against her, and then withdrew the stay, so who knows what will happen.Agreed on CAS - but if the timing is the same (February 2020, December 2020), it seems that next season in the CL would begin prior to a decision, leading to a deferral of any penalty until 2021/2022 CL.
The Swiss Supreme Court reversed a suspension of the IAAF’s ruling that allowed the South African Olympian to continue racing.