The plot could be anything. Some third party we never knew about who were working with the cat people the entire time begins to cause problems. I'm sure we'll get a trailer before too long. I imagine they want it out before the year is up. Likely September. I've noticed when we get a new movie in February for Scooby, another one usually drops in September.
Whatever it ends up being, I'm just not sure it'll be worth it. I feel they are too afraid to have 'real supernatural' stuff in Scooby anymore, and I don't want the same thing to happen that happened in this film.
However if it turns out the KISS sequel and Return to Zombie Island end up being the same movie, I'll buy it day one. The pure insanity of that would be too good to pass up.