There are still some major differences between the early 80s and the current market:
* IBM: They owned the office long before Apple came along and continued that dominance with their invention of PC. IBM isn't in the tablet business. RIM tried to make a play and did poorly. Increasing corporate tablet sales are going to Apple.
* Price: Compared to a Mac the PC was cheap. Nowadays tablet makers are having a hard time building <$500 tablet that will sell.