The only way Bale returns to England over the next couple of years is if he forces a move due to family reasons - ie- his partner wants to get back home. I would be stunned if Madrid forced him out. He's simply too good. If they needed to sell players to fund the acquisition of others, it wouldn't be him. After all, they already elected to sell Di Maria instead of him. I think they'd move Isco or James (the latter of which I similarly don't think they have any interest in offloading) before Bale.
Again, it's too bad, in my opinion. I don't understand those who feel Bale would flop for us. Why would he? He's already dominated in England, and is a better player now than when he left. He's got excellent size, power and pace, along with above average technical skills. He's absolutely tailor made for England and would be a dream signing, both on and off the pitch. As long as we have firm contingency plans, I have no problem if United continues to pursue Bale over the next couple of years. He and Kane should both be targeted.