This would be awesome!
I love being able to get my email, ssh into my machine, browse the web, run SOAP apps, watching pre-recorded TV and movies, listening to MP3s, while I'm out and about. So to that end, I spent major $$$ for a Treo 650, iPod-mini (was a 40GB model), and a Zaurus SL-C760 with wifi/bluetooth.
Now my work stuck me with pager and I look like frickin' Batman (or Choda Boy) with all the gadgets on my belt. If Apple came out with a PDA-type device that integrated with OS X, had mini versions of their stock apps and some iLife apps, and had integrated 802.11g and bluetooth with a keyboard, I could sell all that other crap.
It's gotta have at least a 4-6GB HDD and builtin wireless, though!
Actually, it'd be very cool if they partnered with Motorola to update the A630. I owned one briefly (T-Mob coverage didn't work for me) and loved the form factor, but the software on it sucked. If they redid that model so it had a slightly larger internal screen, OS X lite, and at least a mini-SD slot (or a CF HDD!) that would be cool. That definitely would replace my PDA, cell phone, and iPod.