I'm not sure I can see a Speed Racer sequel, in my mind, but I support you there.
Serenity, bet loads would love that, least there's the Firefly comics.
Incredibles 2 on way:
http://screenrant.com/incredibles-2-cars-3-details/
I know it might not be enough, but least Dredd has a comic sequel, Dredd: Underbelly.