A new report from Geek.com claims to reveal how The Hulk will factor into Thor: Ragnarok next year. Revealing that Hela manages to destroy Mjolnir and banish the God of Thunder from Asgard, the site adds that the hero apparently ends up not on Midgard, but an alien gladatorial planet instead. Knowing he needs to stop her and Loki, Thor fights his way through all of the opponents put before him so he can escape this world, but it's when he runs into the current champion that he gets an unpleasant surprise.
As you've probably already guessed, that's The Hulk, and "he’s managed to avoid reverting back to the Banner state since we last saw him in the Quinjet in Avengers: Age of Ultron. Hulk in Hulk form is pretty much unkillable, so he survived the trip to Sakaar (however he got there). His 'Banner' is starting to seep through into the Hulk persona, and because of the Hulk-Banner melding, Hulk actually remembers Thor and his relationship to him. That’s what starts the two on a Midnight Run to the MacGuffin that Thor desperately needs."