Ipod was released on 10/23/01 and there have been 4 revisions as we are now on revision 5 with the ipod video. That means 4 revisions in nearly 6 years. It has been over 18 months since there was a major ipod revision and the average has been around a year between revisions.
Ipod's are different, the market for MP3 players was emerging. You didnt have to convert people to a service and away from their current device. The VAST majority of iPhones will be people converting to the iPhone, not getting a cell phone for the first time.
As many people are rumoring (that is NOT a confirmation or announcement) Apple may announce iPhone 2.0 in December or January but, as with the iPhone, it may be 6+ months from them before they hit the market. Even if that happens I expect a 1.5 type of upgrade, maybe more memory, better battery, etc. I will be STUNNED if they announce a 3G, GPS unit in 6 months as they would essentially kill all sales of iPhones as people wait for the new version.
Bottom line, 2.0 is coming... just dont know when. A widescreen touch driven iPod has been rumored for well over 2 years.
ash =o)