I see what you're saying, but I think there's one major problem: we're never married to a single interface. I think a lot of the struggle to adapt comes from a certain fear of new technologies and change. It's a mental bandwidth issue for a lot of folks - why should I go through the trouble of learning how to use my PDA when my Day Runner still works?
But learning a new interface for something we're already familiar with, i.e. entering alphanumeric data, requires far less bandwidth. Even less when you consider that the idea of spelling words with numbers on a keypad has been around since the early days of the phone. It's not a radical shift in how things work, like the shift between PDA and Day Runner (how do you flip pages in a PDA?), it's just in how the data is entered.
Most folks interact just fine with the various data exchange interfaces they come across on a daily basis. There's typing, scrawling, talking, body language, symbols and non-verbal sounds. All of these are exceptionally complex, yet we're built to memetically driven, so that won't stand in oru way. I think you'll get the hang of the new phone interface in no time. I know I have, and I'm a 28-year-old geek who's been married to the 101-key board since I was 10.