I would think that the shuttle would survive for some period of time, and even possibley make it all the way back to the cape, although the gear might not be operable at the time of landing...

I would think that the plasma that forms at on near the leading edge of the wings would in and of itself, sheild the door for a time from the highest of tempatures encountered during re-entry...

But the longer the tiles were gone, the more likely that even in the center of the wing surface (where the landing gear doors are located and the tempatures are much lower than on the leading edges) there would eventually be a structural failure of the type that we likely witnessed.

Scott