My own prediction: The Fallout 4 Creation Kit will feel very familiar to people used to the Skyrim Creation Kit.
It will have Scene support, unlike the Fallout GECKs.
Papyrus will be the language, and the assets will use NIFs. (both enhanced, of course).
A lot of the variables will still be 32 bit (bah).
All in all, it will be a nicely enhanced Skyrim Creation Kit, with a lot of the same assets. Even magic...
I really hope I am proved right or wrong - soon. Like this month...