No Thiago Silva, no Thiago Alcantara and a declining Xavi. Next season will be very hard. Winning the league seems impossible.
You are very pessimistic, a lot of people on this board seem to be and I don't know why. Thiago Silva will still sign but PSG are not going to give him away, negotiation takes time. Xavi may not be able to play as often but his best level is still as high as at his peak and Thiago has not yet left and will probably stay and even if he were to leave there are many replacements available.
Barca will win the league this season, I have no doubts about it. Ancelotti is a downgrade from Mourinho and Real will feel it. Barca have Neymar who is the best young player in the world, a player who every club would want. There is still a month or so to bring in players for pre-season and none of our big European rivals have made great signings apart from Munich with Gotze.
Bayern are the only team I would say are better than Barca at the moment but Pep is not a sure thing and they may struggle to perform at the same level as last season. With a couple of signings and a tactical tweak Barca are still the best bet to win the champions league this season in my opinion.
There is not an awful lot wrong with the team and It is up to Tito to fix the small problems and I may be in the minority here but I think he will do it.