Its really hard to foresee, whats going on in his head..he is not easy to judge. IMO its just a matter of time for him to leave Dortmund, as he seems to be the kind of guy, who wants to have a picture book career with elite club, playing abroad, huge money and all that. Cannot blame him and he is in general a smart guy. His 1 year contract extensions also show, that he doesnt want to fully commit to Dortmund, but also that he is not a total jerk, as his contract was running out. I wouldnt rule out him staying, but that looks very unlikely.
His preferred choice in the past has been PD and there Barca, but Real would be nice too I guess. The EPL has been tempting too of course and I can see all of them trying in the summer. I have no idea, if he would consider an offer from Bayern, but I think they ll also try. Dont forget Paris has also tried several times and why should they not try again next summer? Long story short, dont get ur hopes up. I want him too, but I m sceptical.