Apparently half the world is planning to buy a tablet computer before the end of the first quarter. RIM has ordered 1 million PlayBook tablets from Quanta Computer in Taiwan, which it expects will ship before the end of the first quarter.

Motorola is also targeting big tablet sales this quarter, with its own order of between 700,000 and 1 million Xoom tablets. Just how big is the market for tablets?

According to the DigiTimes, "A number of executives from Taiwan-based notebook makers have given recommendations on PlayBook's OS and user interface after they tried on the gadget at CES." RIM's entire CES presence this year was focused on the PlayBook, which my colleague Fritz Nelson spent some time with.

RIM is launching a Wi-Fi-only version of the PlayBook first, with a WiMax 4G variant coming later this year from Sprint. Motorola's tablet will ship this quarter with Wi-Fi and CDMA-based 3G for Verizon Wireless' network. Motorola's Xoom will be upgradeable to an LTE 4G version later this year.

These two tablets will make a big splash this quarter, no doubt, but they aren't the only ones. Apple is widely expected to refresh its iPad soon. Apple may announce the next version of the iPad before the end of January, but it likely won't ship until late in the first quarter if not early in the second quarter (same as last year).

Then there's the soon-to-be-announced webOS tablet coming from HP, which will be revealed on February 9. HP hasn't hinted when its tablet will go on sale, but it is obvious that there's a lot of tablet activity heating up in the first quarter of 2011 -- and that's discounting the dozens of me-too tablets announced at CES.

Will there be enough buyers for all these tablets that are primed to flood the market?