Lost Planet is already in the works. According to the entry, Colonies is a "3rd-person shooter" being developed for Xbox 360 and will be published (in Germany) by CEG Interactive Entertainment, a European subsidiary of Capcom.
The "Lost Planet Colonies" trademark first surfaced in late May, but Capcom would not confirm that a sequel was in development. A few weeks later, Dutch distributor Nobilis listed Colonies as an Xbox 360 and PC release due in January 2008 -- but again, Capcom remained ambiguous about the alleged title. Today's development is the most definitive evidence of a true Lost Planet continuation, but it's still weak. The USK listing could be an error, and instead of a sequel, Colonies could be the subtitle of the meaty PS3 edition of Lost Planet -- or something entirely different, or nonexistent.
Lost Planet was an early success for Capcom's global initiative (though it flopped in Japan), so it seems likely that a sequel will eventually work its way through the pipeline. Still, there are a lot of other Capcom properties that could (even, should) take precedence.