Guardians Of the Galaxy: Volume 2.
At least, that's what Kevin Feige referred to the sequel as when relaying to Collider that the plan was to begin shooting it in February or March of next year. As any fan of the first Guardians Of The Galaxy will know, this is a nod to Star Lord's "Awesome Mix Vol. 1" which provided the movie's excellent soundtrack.
At the end of the interview Steve Weintraub asked the Marvel exec if he had just revealed the title, but he wouldn't confirm or deny it. It's unlikely Feige would have slipped up and blurted this out the unintentionally, so chances are he either planned to drop the movie's official title into the conversation, or he's just messing about and it won't be called that at all! We're sure to find out one way or the other soon enough.
Guardians Of The Galaxy 2 currently has a release date of May 5, 2017.