Boy Genius took a look at his server logs and found somethings (plural!) very interesting -- entries for both iPhone 3.1.3 and... iPhone 4.0!
iPhone 3.1.3 would denote a minor fix to iPhone 3.1 (currently at iPhone 3.1.2), and could drop any time. iPhone 4.0, if Apple keeps to their previous schedule, would get a Sneak Peak event in March, followed by a beta period for developers, and a public release in June or July to coincide with 4th generation iPhone hardware (also already caught in server logs).
No signs, of course, of the still missing-in-action iPhone 3.2. (Where are you?)