Vin Diesel had a few meeting at Marvel, and it was eventually revealed that he will be voicing Groot, the tree in Guardians of the Galaxy, (Personally I would have preferred him as Rocket Raccoon, but what do I know?) but that wasn't all they talked about. While talking to Maria Menounos Diesel had this to say:
"When I met with Marvel it wasn't for anything immediate, it was to talk about a film that would be introduced in the Phase 3 part of Marvel -- not for a few years."
The Phase 3 films he is referring to is a bit of a mystery. He said it would hit in 2016, and then he said the following:
"... something so big I can't even talk about because it's like the merging of brands in a way which I won't get into."
Merging of brands? What could he be referring to?