Caveat: I am a Tottenham fan and don’t want to see Bale leave the Spurs at all.
That said, it does not make sense for Bale to leave for Real Madrid so long as Cristiano Ronaldo is there.
Both players need to have the team formation built around them and the roles of the other players determined in light of supporting their attacking moves and compensating for their defensive deficiencies.
At Madrid, Ronaldo is a one touch, penalty predator who charges into the box from wide, similar, in truth, to Robert Pires in his prime. He doesn’t track back and doesn’t stay wide, so needs a fast, powerful fullback behind him who can cover the entire left side of the field on his own, because Ronaldo does not adhere to any tactical role except for getting on the end of crosses and through balls in order to score.
It’s easy to say, ‘just put Bale on the opposite wing from Ronaldo, no problem.’ But it’s actually a huge problem. With two wide players roaming the field at will, it opens up huge gaps, particularly on the wings, with opposing fullbacks and wide players doubling up on both Madrid fullbacks, who will be isolated by the unconstrained nature of Ronaldo and Bale. Central midfielders can help cover, but that then opens up gaps down the middle.
One anarchic player, if he or she is of sufficient genius to make it worthwhile… well, accommodations can be made for genius, but it is not possible make that allowance for two players without completely disrupting the team’s shape.
Bale, if he transferred, would either quickly be marginalized (brought in for games when Ronaldo was being rested) or else put in a constrained role that did not play to his strengths. Either way, the swashbuckling attacker who is taking the world be storm, would sink beneath the waters.
If Ronaldo were to leave Madrid, absolutely, Bale could go. He could be plugged in, playing as close a like for like as you are likely to see for the departed Portuguese winger-cum-striker, with little tactical tinkering necessary. But until that happens, Bale needs to stay where the team will be built to emphasize his strengths and accommodate his weaknesses. Right now, Madrid is built to accommodate someone else.