It’s PC-based Final Fantasy news day, apparently. Earlier today Final Fantasy IV showed up on Steam, and now NeoGaf has sighted a Steam logo on the Japanese portal site for the Final Fantasy XIII trilogy.
The opening post in that thread also suggests a (PC) platform listing showed up on the North American Final Fantasy XIII site as well, but while that may once have been the case it’s not there any more. That might indicate a mistake, but it may also suggest that this news wasn’t necessarily supposed to get out yet.
I’d speculate further, but since I’ve never played any of the games in the Final Fantasy XIII trilogy I fear my analysis would be close to useless. For anybody who was hoping the games would be ported over to the PC though, it’s looking more likely today than it was before.