Everything depends on us securing CL football. If we secure it this season, I'm absolutely sure Bale will be around till summer 2014 at the very least. I also wouldn't bet against him signing a one-year extension to his contract over the coming summer or as the 2013-2014 season progresses, just to ensure that 'three years on his contract' leverage still exists even if he stays around for another year. Then, everything points to a monumentally profitable deal with most likely Real Madrid, and all parties will be reasonably satisfied. We will have seen him at the peak of his powers for two seasons (this one and the next, which is probably the most we can hope for), Madrid will get a fully developed player, Levy will receive an earth-shatteringly large fee and a 24 or 25 year-old Bale gets to spend the prime years of his career with one of the continent's biggest teams.
Plus, him staying combined with us till 2014, combined with the revenue gained from securing CL football will most likely see us sign a replacement for him (or promote one from the youth team, if we have a spare Bale lying around (
http://bloggar.aftonbladet.se/bankoniva/files/2011/11/ken.jpg), and bed him in over the course of the next season, ensuring the impact of his departure will be minimized.
If we gain that CL spot, this is assuredly going to happen. All I can add to that is that I hope we win a trophy, either this or next season, so Bale has a memento of his time at Spurs.
If we do not gain that spot, however, his future becomes infinitely murkier to predict, and this seemingly unassailable plan will be blown to smithereens.
Sigh. Modern football.