Yes, yes, we know. While some just seem to be figuring this out, Final Fantasy XIII is coming to the Xbox 360 *and* the PC. Square Enix announced this way back at its E3 press conference. Probably going lost in the jaw-dropping Xbox 360 announcement. To review, here's how the FFXIII development cycle is going down: First do the PS3 version, then the PC version and then the Xbox 360 version. And hey, there's been Final Fantasy games on the PC game before, so this isn't exactly something out of left field.
In case you missed it, here's our liveblog of Square Enix's E3 presser. In it, I liveblogged: "kitase says they're currently running it on a pc, so they don't know the work load of getting it on the 360. they are putting priority on the PC version." Also, here's a link to a post on the Nvidia site about the PC version.
Update: We contacted Square Enix, and according to the company, "The game is being built using PC-based development tools, but that doesn't mean it's being created for the PC platform. Our current plans are to release FFXIII for the PS3 and Xbox 360 only. Sorry for the confusion!" So to recap, it's being created with PC-based dev tools, but with plans only for PS3/Xbox 360 console release.