Have the old uptodate url always say you're out of date?
If you go to https://check.torproject.org/?lang=en-US&small=1&uptodate=1 over Tor, it will give you a comforting message about how you're all set.
But the only things that go to that URL these days are out-of-date TBBs, some of which have various bugs that prevent them from recognizing that they're out of date.
Should we just change the page to tell everybody that they're using an old TBB and they'd best get a new one?