that OS X 10.2 gets renamed OS X 10.5 by the same marketing group that decided OS 7.6 should get renamed OS 8.0, OS X Public Beta 2 renamed to OS X 10.0, etc. By making it a .5 release, they can probably get away with a minimal ($49) upgrade fee. From what I've seen of the feature set, I doubt they could charge much more than that. They'll probably run in to lots of whining either way.
Personally, if OS X 10.2 doesn't have USB Printer Sharing, Labels, Spring Loaded Folders, and Appearance features ala OS 9, I'll be quite disappointed if they decide to charge for it. From what we've seen of 10.2 so far, it looks like Spring Loaded Folders are back, but I haven't heard anything on the other features. Plus with the amount of time they are taking on it, it should be chock full of new features....