TechCrunch is reporting that Barnes & Noble might be at The Unveiling on Wednesday. Erick goes on to speculate that the B&N ebookstore might even be integrated into the new tablet as the ebook reader. I highly doubt it.
Look at the iTunes model as it applies to music. Apple deals directly with record labels and takes a 30% cut of the retail. Apple is rumored to have met with publishers last week, so there is a better than even chance that Apple will offer them a simliar deal (Amazon sure thinks so). If Apple deals directly with publishers, then why would they need B&N?
There's an excellent chance that existing apps will work on the the new tablet, so it should be able to read ebooks from day one. But that's not Apple's long term plan. Apple wants to sell you stuff directly, not work through someone else. If there is an ebookstore integrsted into the tablet it will be an Apple store.