Why is everyone so sure his end goal is to play for the NT? He doesn't get money out of it nor is Germany likely to win anything right now.
At Barca he receives a huge salary that no other club will match, lives in a nice city, Barca is likely to win the CL based on last season's performance and apparently he found a new local girlfriend.
I somehow doubt his priority is German NT, so much so that he'd leave Barca for a midtable club just to get minutes so he can secure a spot for Germany. Chances are high if he leaves Barca that Germany loses and he gets all the blame: "See, no wonder Barca got rid."
I think he'd rather receive his Barca paycheck, call in sick and enjoy life in Barca as long as possible.