I was digging through the software matrices today and stumbled across this:
Looks like those users who can't (or won't) make the jump to Creo Parametric 2 (or later) will need to stay at Windchill 10.2.
No surprise there.
Creo/Elements Pro 5.0 has an end of life date of September 2015.
Windchill 10.3 has a release date of Q3 2015.
Why put a dead product with a new one and do all the testing.
Also notice that the actual MR of Creo2 and Creo3 has not been determined yet for Windchill 10.3.