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 own a Blackberry 9700 which was a nice phone when it came out but have been underwhelmed by the 9780 and in some ways even the 9900 (no autofocus camera, no UMA). That's why it's the first thing I thought of.
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.