So how is this gonna add up in Thor: Ragnarok. First question would be why Hulk in even in it and how big it’s role. Highly doubt would be a small role and take note that the plot has not been fully revealed. So far what we know is that Loki shall return and the movie will continue right after the Avengers: Age of Ultron event. In Avengers: Age of Ultron we saw Thor when to Norn Cave where he had some visions. The full vision for some reasons didn’t get on screen but however the deleted scene was made available on Bluray/DVD.
As for Hulk’s part, at the end of Avengers: Age of Ultron we saw him in a Avenger Quinjet. All soft and curled up trying to get away to somewhere that we don’t know.
As for Ragnarok, we know that Lady Sif will be in it and possibility of Captain America(Read Here) but how is The Hulk gonna be in is really a mystery still.