So far there have not been any problems for Man City or Real Madrid in the group phase and both have packed full points in every match which has made them both lead in the standings. Bayern Munich is a little more promising this season than before and the arrival of Harry Kane has made their front line sharper, making them now one of the favorite German representatives to compete with Man City and Real Madrid.
I also want to include Inter Milan as the Italian representative who will fight for the title and finishing as runners-up last season will provide great motivation for them to continue to advance to the final this season. Even though it looks difficult, nothing is impossible because Inter Milan has a strong defense when they face a big match in the Champions League.
Moreover, if the four teams you mentioned above do not face each other in the knockout rounds, I would also like to say that the teams that will enter the semifinals will be Real Madrid, Inter Milan, Bayern Muchen and Man City. Next, the Real Madrid vs Man City team will enter the final.
However, in my opinion, Man City will become champions again, just imagine when the team is losing its pillar players and there is a storm of injuries but Man City's game is still dangerous for every opponent. This is just my prediction.