I don't think Real Madrid, Manchester City and Bayern Munich will be making big transfers in January which could really have a big impact on their title chances.
I have mentioned these 3 teams because these teams are the top favourites for the championship in the Champions League (according to bookmakers I mean). I also agree with this classification honestly because they are technically the strongest teams with the best squads. I don't think that any of them will feel any weakness in their squads much. Real Madrid could make a transfer for the defense line though. Because Alaba has also got injured so Ancelotti needs to strengthen the position.
Even your all statement is good and acceptable with most chances Real Madrid and Bayern Munich will not go into transfer market for any change, but Manchester City can go because they are facing poor time with their two-star players are already injured and this is hurting them badly hopefully they will try to have suitable players which can give them better results in absence of these star players which is surely going to improve their depth in coming weeks.
Alaba injury is not series with Carlos Ancelotti already announces he is happy with his team, and they will not go for any change or any player in this winter transfer window now just few days left with we are going to have another action-packed half of the Champions League is going to play.