At the same time, the top-50 (or -whatever) institutions have the least incentive to rock the boat: they're usually rolling in "buying power" :) and their faculty are relatively likely to be among the winners of the game as it's currently set up (negative-sum game though it is). I think it's safe to say that if the top 50 were sufficiently motivated to make closed-access journals go away they would already be gone by now.