Phht, hecks no. They built a really reaaaly interesting and well though out universe, it’d be a huge injustice not to keep going.
It’s like Toy Story, they’re endless possibilities, for example, what if some hacker-douche tries to run the arcade out of business and rips the data off the cabinets to be made into an emulator? Ralph and the gang wind up on his computer with a bunch of other disenfranchised characters and have to stage a rebellion to escape!
The characters in this movie are literally made up of bits of data, that’s a crazy awesome concept and they could go a ton of places with it.
Anyway, the problem some people have with the “Sugar Rush” part of the movie is that at a point in the middle it feels like they forgot it was about video game characters and it turns into a movie adaptation of Candy Land. Between the point when all 4 main characters arrive in the game and King Candy talks to Ralph about Venelope being a glitch the movie feels kinda unfocused. It was still good, of corse, but it kinda felt like they had forgotten the premise.