Don't think so with the new Metroid coming out soon. Metroid: Other M for the Wii.
Edit by Phazon lord on 4/27/2010. They were rumor's of a direct sequel to fusion called Metroid Dread but it is almost surely non existant. As for MZM, its just a remake of the original metroid so technicly, the sequel would be Metroid prime 1 when it comes to story line.