Well prime is all about "Metroid Prime", and the storyline surrounding that. So I would imagine they would come up with a new storyline involving samus as a bounty hunter, but keeping close ties to the fact that it is a Metroid game. The design of the new game is interesting for samus as it opens a few options they never had before. By being able to move from planet to planet (especially if this is a player choice) it seems possible that we could see either a different kind of metroid in the future or just a spinoff series. We might even see some more zero suit samus in the future. Honestly, it is hard to say where it is going but I think they have done a good job of leaving themselves open to new possibilities.

They'll just start a new trilogy with similar gameplay.

At the rate Metroid games come out, they got plenty time to think stuff up.

Metroid 5 for DS.

Probably a new 3rd person Metroid on the Wii before th console's life cycle is over.

Possibly a Hunters sequel for DS or Wii.

I wouldn't be surprised to see Metroid take a little break and for Retro Studios to work on other properties ...

I'd like to see what else Retro could do.

There will be a new Metroid, it'll just be called differently. (i.e. not Metroid Prime, but Metroid idontknowwhat) This new game may change the gameplay a little (for example it could be third person), but it could also feature the same gameplay and just offer a new storyline.

If the Wii lasts more than five years, we will probably see it on the Wii. Maybe we will also see it on the DS, that's very difficult to predict.

Depending on how much projects Retro Studios have in their hands, it could also be that another studio takes care of the next Metroid.

I am betting we will not get anymore Metroid from Retro. The next Metroid will probably be a new twist to the game and include more space travel. Like a game where your are finally putting an end to the Space Pirates, but you have to travel from world to world shutting down operations.

Anywho, that's just my two cents.

nSpace (the makers of Geist) have been MIA for a little while now ...

It was rumored that Nintendo liked the studio and thought that they had a lot of potential and I think with guidance (from Retro and Nintendo) they could be a potential candidate for creating further Metroid games. Many developers produce average games because they lack interesting ideas or don't know what would make a good game but I think that nSpace primarily lacked experience and leadership and could be made into a world class developer under the right conditions ...

would be interesting to see a n-space Metroid game. Is there a direct connection between them and Nintendo or does it depend on the will of Big N if they can develop first party games?