Phone, ok, table, ok, TV/media center, ok, Desktop. wow, now you went to far.
I suspect we may need to wait for Project Denver and ARM-64 before having the smartphone take over the PC. I favor Ubuntu as my desktop so it is not that far out for me in terms of OS.
However, the electronics will become relatively cheap, and they in fact are kind of cheap right now, a $200 tablet is very cheap specially if you see the price of electronics over the years accounting for inflation. So it is more likely you'll see an ARM chip thrown on any future media device instead of trying to turn your cell phone into multiple devices.