From an office/work environment point of view, I think it's quite a feasible idea. However, from an enthusiasts point of view, I don't think it would be a welcomed proposition.

Personally, I'd still want a desktop PC, no matter what the capabilities of a smartphone are. I like to dabble with my PC and upgrade it, the next thing on my list is a new CPU. I'm also a gamer, and I'm already at a stage where games that were released last year give my PC the sweats unless I upgrade.You simply won't be able to do this with a smartphone, you'll be effectively stuck in laptop linbo where everything is based on SMT (Surface Mount Technology). No CPU upgrade, no video card upgrade, no sound card upgrade. Unless of course someone does actually take the initiative and produce a modular design where the CPU, video sub-system, audio and maybe the internal storage can be swapped out.
Technological progress in the computing world is moving at a phenomenal rate and I believe that making such a bold move as replacing the home PC with a smartphone that can do everything will hamper the progress severely, if not stop it completely.

I don't intend to p**s on anyone's bonfire, because there's things that I want my N900 to do that would be great time savers if they were successfully implemented. Like sending a document to a Bluetooth/wireless printer, read pen-drives, external optical drives, hard drives, keyboards, mice, projectors etc.
Thanks to you guys (the "ENTHUSIASTS") we're almost there. At the rate you're going when Nokia do finally drop the first Meego handset us N900 owners will still be doing things that even that handset can't do.