The iPhone 4 seemed like a huge step up from prior models to me thanks to a 326 PPI display, a much faster processor, and a variety of other reasons. I guess even Apple acknowledges this given the naming convention of going from 4 to 4s. Not enough of a change to warrant iPhone 5.
This is just like the iPhone 3G > iPhone 3GS transition. Doing a new enclosure every year would be pretty taxing, so they take a year off. Incremental hardware improvements meanwhile. The funny bit is they barely needed to do this much — iPhone 4 was still selling steadily.
I think I would prefer an iPhone if it were on T-mobile or if not that, at least the option to buy an unlocked iPhone at a reasonable price that worked at reasonable speed on T-mobile. Not so with today's announcements. An iPhone 3G can be purchased unlocked for $375, or an iPhone 4 for $549 but both are very slow on T-mobile at EDGE data speeds.
An exciting announcement for me personally would not have been a new enclosure, but rather the ability to run on T-mobile at fast speeds, all at a reasonable price. Wishful thinking, I guess.
I suppose I also had a good idea about what would be announced thanks to MacRumors accurate reporting, so I wasn't let down that the phone is called 4S instead of 5 (besides, I love the iPhone 4 external design).
This cycle is pretty clever as it pretty much guarentees majority of iPhone 4 holders will upgrade to iPhone 5, whilst simaltanously giving a decent bump in sales to people who have had there friends talking up the iPhone 4 for a year a chance to one-up them.
All the Australian networks are moving to 4G, so IMO it's a good time to wait for the next gen of LTE handsets. As with the original iPhone, I suspect it was just too early for Apple to switch.