I think PTC will be following a similar pattern to Solidworks in releasing maintenance versions.there will be only upto CREO 4.0 M060.which means only 5 maintenance releases for CREO 4.0. Maximum bugs won't be resolved.
Then a new version will come up adding the old unsolved bugs and then the bugs from the new version.
This same process has made solidworks current versions horrible.
there will be two tracks if i remember correctly, long term support and the "usual" one (where the product becomes unsupported with the release of the next version).
i think that creo 4.0 is supposed to be the long term track.
i don't have access to ptc support so i can't confirm it