The already-considerable popularity of the Guardians of the Galaxy franchise will inevitably spill over into Infinity War, but where the group goes beyond that is anyone’s guess. If Gunn continues to put out quality work with the series and still desires to make a spinoff with Rocket and Groot, there’s little reason to believe the spinoff wouldn’t one day become a reality. The duo is certainly the kind of team-up that would work well in their own adventure.
As for Groot battling the Hulk, it’s unclear how serious or knowledgeable Diesel really is on the subject. But if the fight really is going to happen, it would likely take place in Infinity War or the as-yet untitled fourth Avengers movie in some capacity. Diesel’s “poster” comment implies that the two would get yet another spinoff of their own, but that seems too far down the road to predict at this point. What’s certain is that news of an official Rocket and Groot spinoff would likely be well-received.