Probably the only update that we will hear on the 20th is how many they've sold (I think would be highly unlikely due to the quarter release on monday) and possibly an update on an official release date for iOS 4.2
20th event will be about OS X 10.7 "Lion" (You can see it on the invite) and maybe some Notebooks refresh, Noting about iOS related (that include Apple TV, iPad, IPhone, iPods)
go get a iPad now, so you can get 3.2.2 on it and JB 😀😀
It's an existing product with active sales, there's not going to be a two-month-lead announcement for the next iPad. It will be announced when it's ready for sale.