I believe there will be an iphone, but I doubt it will be a smartphone right out of the gate.
Not to be too skeptical, but look at how long and how much R&D goes into current smartphones (especially qwerty ones). There were leaks for MONTHS before the E62, TMobile Dash, Blackberry Pearl, Treo 700p/W/750v/680, HTC StrTrK, etc all came out, because these things don't happen in a total vacuum...all that testing, it's hard to keep tongues from wagging and secret cameras from snapping. And people are certainly on the lookout, so it's not like Apple would fly under the radar.
A mobile OS smartphone has to stay connected to a server or connect quickly, multitask (at least enough to connect, etc while doing other things), sync efficiently with other computers (probably Macs and PCs), play nice with cellular-type things like texting and voicemail, and really just overall be stable while being super portable and able to function as a lightweight OS. It's definitely possible, and probable. BUT I think Apple will probably release a plainer iPhone first, probably running their mobile OS X, run out all the basic bugs that come from a phone, then release the smartphone version. The smartphone market is cutthroat, very competitive. It's better and more prudent for Apple to play the field and then come out swinging. Look at Motorola...they tried with the MPxx series, screwed up royally, pulled back and focused on their hardware, and then came out with a home run in the Q.