Don't think there's a mention on Bild and this makes no sense right now. Kroos is leaving so he has less competition, Lewa is coming in which helps his game, he seems pretty settled, and he's generally popular among the entire Bayern team (and plus he now has another Spanish buddy in Bernat). As Jamdav said, if Barca starts succeeding again over the next few years then he might be tempted to return with his brother here but it's just rumor spitting at this point.
Considering that he likely wouldn't want to come until 2-ish years from now, I wouldn't want him to come back at all as it just complicates things like Cesc did. We've got players like Kaptoum in the pipelines, Rafinha still hasn't found his role yet, and he's not gonna come for anything less than a fortune at that point. It's not gonna happen this window so it should not happen period.
The rumor itself reeks of bullshit. Thiago's biggest worry right now should be to stop getting injured every 3-4 months and to cement a starting position now that he has a chance for it. Things are fine for him at Bayern and I'm pretty sure he sees it that way as well. My main hope for him now is in perspective for the NT, which he'll be an important player for soon (barring yet another injury). Funny seeing the reactions here after so long though