They might get to them sooner or later. Sometimes it takes a long time between sequels getting riffed because they want to make sure the material is fresh. There was a big gap between the last two Harry Potter riffs for example. We're also still waiting on Return of the King. Then again, they've also said that riffing one movie in a series is no guaruntee they'll riff them all.
I wouldn't mind seeing these two riffed either. Though I liked them on thier own better than a lot of people, they do both seem to have more riffable material than the first one, and the first riff was fun.