Whatever Bungie's latest project is, be it a Sci-fi MMO or not, the team are currently looking for beta testers, as advertised on their website. I'd imagine there will be quite the influx of requests, but it might be worth your while giving it a try.
You'll have to go through a survey of your gaming habits and what not - we'd imagine that Bungie is looking for a wide spectrum of different types of gamers, so this probably isn't the time or place to boast about your mad Team Fortress 2 skillz.
The project won't be a Halo title, Microsoft's 343 Industries is now in control of that IP, but we've heard reports that it'll be a shooter, with RPG elements set in a persistent world.
Time will tell.
Bungie Relaunches Its Beta Tester Program [MTV Multiplayer]