@JohnAskew: There is either something in there very cool that they're trying hard to keep back till the last possible second, or they're taking full advantage of all the speculation to build up a certain amount of hype (which is actually kind of working judging by the amount of WP8 speculation around).

I suppose the last possibility is that it's an agreement with existing WP7 supporting carriers to try and prop up availability of new WP7 compatible apps up to and beyond the launch of WP8 (after all, they are still selling those handsets right now). I think that's a little too short term to be a viable justification though.