Unless your name is Kevin Feige, you probably know next to nothing about what Marvel has planned for the mysterious Phase 4 (or whatever it will be called) of the Marvel Cinematic Universe. The only clue we've gotten is that the MCU will be going hard on cosmic stories in the future, but apparently, that means that Marvel could be eyeing Rocket Raccoon as a major character to take us through the next batch of films. The manic smart guy of the Guardians of the Galaxy could have a big role to play, as indicated by some specific phrasing from James Gunn. Responding to a question about Rocket, Gunn said...
As you know, the MCU is one way of processing these characters. 616 is a different one. We are going to learn more about where Rocket comes from in the coming sagas.
James Gunn was in attendance at the Hasbro HasCon (via MCU Exchange) when, while at his panel, someone asked him if Half-World (Rocket's home-planet in the comics) could make an appearance in a future movie. Obviously, Gunn isn't going to give away much, but he did say that the MCU will likely do Rocket's origin a different way than the comics. He did say that we will eventually learn more about Rocket over the "coming sagas." It's that "coming sagas" part that's got us interested. While it could be a colorful choice of words, sagas seem to indicate more than just Guardians of the Galaxy Vol. 3 in Rocket's future. It implies that Rocket could have a presence in multiple films to come, meaning he could be a big character in Phase 4.
As to what these films could be is anyone's guess, but there are certainly options. The Guardians of the Galaxy lineup will be changing after Vol. 3, but it's possible that Rocket will stick around for more Guardians movies. There have also been very mild discussions about a Rocket spinoff film. Another option is that Rocket will appear in films outside of his usual series, whether it be a cameo or something bigger. It's just speculation, but keeping certain characters around as familiar figures makes sense.
In regards to Rocket's origins, we already know the basics: He was just a regular raccoon who got kidnapped and illegally experimented on. His movie origins will differ from his less serious comic origins, but James Gunn assured that we'll learn the specifics eventually.
It's going to be a little different from the comics. We already know a lot about where he came from. It's a little bit more horrible than what it is in the comics when you come down to it. We will learn more about that.