Couple of points - firstly, Apple would never use WWDC to relaunch the unibody mac line... It is a DEVELOPERS conference, thus the focus is always on the iPhone or software element (or at least it has been the past few years). We are more likely to get a keynote from Jobs after his return telling us about any new MacBook lineups. Ideally, Apple would go with (this is in Aussie dollars)
MacBook Pro (unibody) 13, 15 and 17 inch - $1999 to $3999 - would allow Apple to stick a faster processor in the 13 inch unit and some optional graphics, without dropping the price in line with exchange rates...
MacBook 13 inch - $1399 - The white model. Substantial price drop, same insides but expanded to include 2 or 3 models... ie a 2.1GHz, 2.2GHz and 2.4GHz...
MacBook Air 13 inch - $1999 - Price drop, similar design, perhaps some more black plastic on there somewhere (base, bezel). Very similar insides...
MacBook Touch/Tablet/iBook 10 inch - $999 - New product which would be the focus of the keynote. 10 inch multi touch screen, aluminium and black design with full glass face. No physical keyboard, Atom processors, 2GB memory, options of SSD or 1.8inch HDD's (so 64, 128GB or 120GB). Introduction of suite of apps specially made fore larger touch screen device, such as advance handwriting rec, notes apps, eBook reading app, diary etc... Would also open up a whole new segment of App store, for more substatial apps, office suits, touch painting tools, touch video and image editing etc...
Also - The Aussie dollar dropped heaps, and Apple released the new line of products at its worst point, making them horrendously expensive here, but it's back from about 50c to 70-80c, which is likely why we got a price drop.
Also - I really doubt that Apple would come out with a 16" laptop/notebook... They love their parts sharing, so would just use the 15" screen out of the MBP... And I doubt they would do a cheaper 15", it's part of the incentive to pay the extra for the MBP (you have to think like Apple here... There's money to be made!!)