Thiago is not yet a Bayern player, I'd say its a transfer triangle, if Thiago was going to sign for Bayern today then why did Pep come out and show his admiration for him and try and sweet talk Thiago to Bayern,
Thiago can either stay at Barca, the club that made him and the club that will give him best opportunities for future spain caps, plus he will play with players he knows and with a style that suits him, however he will have to be patient until Xavi declines before he can make a major impact there.
He can go Bayern, to his former coach Pep, who trusted him and admires him very much, also the best club in the world at the minute and pretty much will win a lot of trophies and deliver much success, however the competition at Bayern is huge and he maybe pushed out to play in positions not optimal for his progress, with lots of pressure to perform.
He can come to us, a team that is dying for a player like him and as long as he plays to a certain standard will be guaranteed starts and playing time due to lack of competition, he would play in his optimal position and not have to be patient, however Man Utd do not play tika tika and he may find it difficult to adapt to the PL.
Lets just wait and see, my bets on Barca convincing him to stay.