Not only Barcelona because all the teams who play in the Champions League also expect the title they can get but the extent of the team's strength in competing for the title. Both Barcelona, Manchester City and Real Madrid will both struggle to get the best results in the Champions League but a number of other teams are also promising because in the transfer market they have brought a number of players to make the team stronger. PSG also tries to maintain the title even though it looks not easy because competition will be far more competitive next season.
It’s worth mentioning that besides PSG wanting to defend their title, there are also Liverpool, Arsenal, and Bayern Munich. These are very strong teams as well, and they will definitely want to compete for the Champions League trophy. All the teams are very strong, and for now, it’s hard for me to pick a single favorite. I see that Real Madrid worked well in the transfer market. Additionally, Militao and Carvajal have already returned to play, and Mbappe will be back very soon. So Real Madrid could be a very formidable opponent this season.
What is clear is that the Champions League competition is very difficult to predict because all teams want to give their best to get the Champions League trophy that every team participating in the Champions League dreams of. However, of all the teams you mentioned, in my opinion so far only Real Madrid has experienced a very significant change under their new coach, Xavi Alanso.
In the past, when I watched Real Madrid, especially when they played against teams at the same level as them, the coordination between the lines of players was far and unconceptual, basically when watching Real Madrid, especially Real Madrid fans must also feel worried. But now in the Xabi Alanso era, Real Madrid's game is calmer, the defense coordination is also solid, especially as you said, Militao and Carvajal have recovered from injury. In addition, under Xavi Alanso, Real Madrid's game often puts pressure on opponents by playing the ball position in the opponent's third area.
So with many positive things since Xabi arrived, they will be my favorite for next season. Because so far I see Real Madrid showing significant improvements from dead balls, corner kicks, free kicks, and crosses into the penalty box becoming much more effective. And I like Arda Guler's role, especially Federico Valverde who is more in the penalty box and has a shot on target, I'm sure he will score many goals this season by playing in that role.