In an interview with developers of Starhawk, a lot of information was revealed to the public.
First off: The game is not a sequel, but a spiritual successor with the same fast-paced gameplay as Warhawk. Furthermore, much like the first, it is focused on the multiplayer aspect of the game more than the single player.
While on the subject of the single player aspect of the game, the single player is only available because of the consumer, something that the developer wanted to thank them for. The strong sales of Warhawk made way for more content in Starhawk. Not only is there going to be a whole single player aspect of the game now, but all of the previous aspects of the game are upgraded and believe when I say that “They look spectacular!”.
When asked about the launch date of the game, the interviewee could say nothing more than “The future. Sorry, if I said anything now it would be the end of me.” So, we'll be lucky to see Starhawk somewhere in 2012.