There have been rumours pinning the releasedate of the tablet to somewhere in the fall of 2009:

http://www.wired.com/gadgetlab/2008/12/rumor-large-for/

So it wouldn't surprise me one bit if they delayed that for a couple of days just to be able to steal microsofts thunder.

The general reception of the latest batch of 'mac stuff' was pretty underwhelmed, if they top it off with a tablet then that will turn around to endless press coverage.

Competition is good.