Not sure I need to spoiler alert a book that came out over 50 years ago, but Momoa should be back in Part 3.
I assume Villeneuve got the deal safe for two parts but the numbers don't justify a part 3.
Maybe a TV show could raise more awareness.
That doesn't mean they'll go all the way to God Emperor, but I don't think we know for sure they won't.
I also doubt they'll go for 3 because all following books don't have that kind of action flick / visual extravaganza potential and this is what Villeneuve can do. Instead there is a lot of talk and this is what Villeneuve can't do. It'll still be the same ol' Dune with a lot of chamber play. I doubt he's even seriously interested in that.
Children takes a sharp turn with the whole possession thing and then Leto's metamorphosis. But Messiah is quite adaptable and is the real ending for many of the same characters as Book 1.