By reading between the lines of the Prime and 30th anniversary panels it looks like the new transformers series will be a continuation of Prime with most if not all characters returning. Fingers crossed it is as this is a good series (needs more characters though).
It's rumoured that the next series will be 2D animation, which would make it cost effective to add more transformers to the cast.
The US airdate has now been announced - October 4th on the HUB, which will mean the DVD will be released 4 days after that for anyone who missed it or want a legal copy of their own.
Don't check the link if you are avoiding spoilers.