Ah, game developers (especially EA game developers, of which id software's John Carmack is now one, after their announcement at E3 that they'd work together to publish games). They thrive on hype, and live, it seems sometimes, off of speculation. That's probably why Carmack has told Forbes that not only does he love his iPhone, and not only does he not want to "announce anything specifically," but id wants to make a game for the iPhone and "it would be," according to Carmack, "a graphical tour de force." See what we mean? Ah, game developers.
Anna Kang, who's the president of id Mobile (no relation), says that any id game they might be working on for the iPhone wouldn't be a new IP, so that puts it very much in the range of a Doom, Wolfenstein, or Quake game, and considering that another Wolfenstein sequel is being worked on right now, that probably makes it the most likely.
For his part, Carmack sounds really excited to have the iPhone as a platform (especially since he hasn't always seen eye-to-eye with Apple) -- he equates it in terms of power to a PS2 or Xbox, and says that a company could easily shell out $10 million on an iPhone game, be it a first person shooter or a deep MMORPG. But he admits that the 99-cent sales in the App Store can't support that yet, and it probably wouldn't be the best thing for id Mobile to pour their resources into something like that quite yet. Nevertheless, we'll wait and see what they come up with.