I'd be really surprised to see Apple interrupt the coverage of the iPad. We're about to see a whole new marketing push to show off the benefits of the 3G iPad, the announcement and preview today of OS 4.0. An international release for the iPad, all this month... that's enough to keep the news on Apple and its products. New iPhone in June, and probably the actual released of OS 4.0 around that time. That really leaves the month of May as sort of open for Apple, and the release of the new MBP might coincide well during that time to keep the news on Apple.
I think we're probably about to see the end of the Air. I know there are people out there still appalled at the idea of the iPad, but I've used mine for work all week now instead of my laptop, and I think for business travel it already offers a lot of things people enjoyed with the Air. True multitasking and some more productivity apps and it could be a suitable replacement for many users. Obviously not those that need high powered specs for serious CPU crunching applications, but those specs aren't really found on the Air either...
I have no basis for this prediction what so ever, but I'm going to predict May 11, 2010.
*If there is any one thing that might make an earlier release more likely, in my opinion, it is the tendency for laptops to be given as gifts to graduates and we are fast approaching the season. That might bring them out sooner, but I really think a May release is in our future.