According to Tony Cervone and ComicBookMovie.com, a follow-up to SCOOB! is coming out soon! Here is a quote from Tony's interview with CBM: "Actually, we are kicking the tyres on a follow-up to Scoob! It hasn’t been announced yet, but it’s something we’re all excited about. The whole creative team that made the first movie is still around and back and working on something new. It was neat to create this Hanna-Barbera Cinematic Universe, and it’s exciting to return to it."
I'm really excited for this follow-up! Notice that he did say "follow-up," not "sequel" as the CBM article says, so I think it's very possible we could get a SCOOB! television series instead of a second film.