IMHO, I don't think it's going to make any difference whatsoever to your chances whether or not you tell them anything, though it is likely that it might piss them off a bit to hear about your acceptances from other places.
you really are desperate, than you could bluff, by saying that you've gotten into another place which needs you to let them know by 20th Feb (say) if you're to be considered for some X fellowship. You could then ask Princeton to tell you if you are likely to get in or not, as you have to inform MIT of your decision soon. However, I'd strongly
advise against any such double-guessing smartassery as it doesn't do you any significant good anyway, and is quite likely to backfire and screw you up badly. Why not leave well enough alone, and just wait a couple more days like the rest of us
Good Luck !