Make no mistake: There's a full-blown battle on for the future of computing.

Forget all the fragmentary skirmishes for your pocket, for your set-top, for your living room, and for your desk.

It's become increasingly clear that the tablet is the defining device of the next couple decades of computing, as the PC was in the '80s.

Handheld touchscreen devices are the key way we'll consume content and buy things.

So that's extremely interesting to anyone who makes devices, serves up content, or sells things.

In other world, the entire technology universe.

Four unlikely contestants—only one with any history as a PC maker—are gearing up to unleash new products this fall.

Why now? There is, as always, the unmissable selling opportunity in the coming holiday shopping season.

But as the New York Times notes, Apple is also setting the agenda for its rivals, with Amazon and others rushing to announce their products before new iPhones and iPads hit the market.