The 2011 MBP could drive two 2560x1600 displays (chained) through a single port, which requires about the same bandwidth as a single 3840x2160. So I don't think that would be an issue, though obviously the GPU is still a limitation.

I appear to be hellbanned from posting links, but I gather this from page 8 of AnandTech's review of the Thunderbolt display and the Wikipedia article for DisplayPort.