The caveat here is that if you make yourself a +3 and you have large-scale downstream consumers, you might be impacting them adversely. For example (not to pick on DTP, just to grab something that WTP and TPTP both require)... if DTP decides it's a +3, then everyone that consumes it must also be +3 and we're back where we started with everyone +3-or-more scrambling at the last minute. If projects who had no problem meeting the +2 deadlines stay as +2, then the projects built on top will simply get an extra couple of days' grace.
But if you're the end of a stack and just want more time, there's no harm IMHO in asking for it by upgrading to +3. There's also no harm in releasing early. Because UML2 Tools is a +9 and GMF is a +8, EMF strives to release the day BEFORE +1 so that all the GMF deps can be done sooner. You're not actually losing time by releasing early, you're just shifting it back slightly.
So, to borrow a line from Indianna Jones 3, choose... choose wisely. ;-)