Most people are consumers - throughout the history of the home computer, they've been bought with the excuse of learning technology, but end up being used for games (80s and 90s) and web browsers in the noughties.
The social media explosion has given a new use for home machines, but the screenboards are enough for telling everyone that you're going to the loo.
Beyond that, bluetooth mice and keyboards are not hard to find (and most folk I know with tablets actually lug both round with them)
Games - the obsession we have with farmville, bejewelled blitz, angry birds etc, shows that lavish, multi-dvd games that require bleeding edge hardware are of interest to a minority only (and current phones/tablets aren't particularly short of processor power anyway)
They all now automatically work with things like airplay/dnla, so streaming to your telly/audio device is not an issue, and easily setup, so you can enjoy the torrents you're consuming on your plasma telly, not the 7" screen.
The only real issue is the lack of local storage, and most of Joe Public have no problems with cloud storage, and it will only be refuseniks like me that sync to a local nas-box, but again, this is not tricky.
Yep, I can easily see the benefits, and can easily see that they will take over, and sooner rather than later - I'll probably keep my current set up for a few years, but will get a tablet soon, and I'll bet large sums of money that it will rapidly become my primary device.