GURPS books that are the core of my campaign include: Cops, Covert Ops, Espionage, High-Tech, Modern Firepower, Special Ops, and SWAT. If SJG would come out with a 4e book that covers all of those, I'd switch over to that version in an instant.
I have this idea for a near-future sci-fi campaign. It would be set in near-Earth orbit, but that wouldn't really limit the setting. First of all, you'd have Earth, orbit and the Moon to play with. Second, there's about 2000 estimated NEO (Near Earth Objects - asteroids, dead comets, and so on). In fact, some of these NEOs would be easier to get to than Mars. Add in the fact that many astronomers believe that Earth has Trojan Point bodies like Jupiter and you've got a huge setting for the campaign. And you haven't even left the immediate neighborhood. Add in Mars, the Belt and Jupiter's huge system of moons and captured objects and you've got a really interesting place.
I don't know if I'll ever run this, but its one of the items in my idea file.