Metriod Prime 8

It's practically impossible to tell exactly which direction the series will go, so determining exactly how the game will be 5 sequels later is impossible. We could easily list the things they MIGHT improve upon each game, such as graphics, sound track, weapon selections, larger planets, longer story, online multiplayer ect. But that's assuming that the series does not take any drastic turns or changes and takes the "increase everything per sequel" route.

But lets be honest, MP8 will probably be released on the next next generation console (basically the Wii 3).

I am of course assuming that Metroid: The Other M is not part of the Metroid Prime franchise. I'm pretty sure that game is supposed to be a spin off instead. Looks awesome though.