You can also extend your storage space with a fairly large SD cards nowadays.
I think the main issues will be RAM and display size.
1GB of RAM is very little nowadays for typical desktop/office use-cases. I was using a laptop with 2GB of RAM until recently and just having Thunderbird (with lots of mails) and Firefox (with lots tabs) open it gets really slow with swapping when I try to view (with OpenOffice) some docs I get in mails...
Phones are unlikely to get a lot of RAM soonish because with larger amounts of RAM, the RAM refresh eats too much battery and the phone SW itself works fine with 1GB (or even 0.5GB) of RAM.
If one uses just Browser, like was assumed in the Moto case, I guess 1GB is mostly enough (now that we've gotten mostly rid of Flash).
The display problem is that the embedded gfx chips in the phones are intended for smaller resolutions. If you connect them to a full HD display, either you got something running on non-native resolution which looks unusably crappy for day-to-day work, or the resolution may go over the phone GPU capabilities or what its 3D driver has been tested for.
I think on travels having just phone, a smallish wireless keyboard and larger display at hotel / remote work place may be fine as phone+netbook combo replacement, but for day-to-day work it's not enough.
Security is also an interesting question... Companies typically require laptop disks to be encrypted, but how well phones work with encrypted file systems? (giving password to mount the disk etc)