Going by my experience with Developer Preview 3, Lion is nowhere near ready to be launched to the public.
This.
Safari went from a Crash-Spam-Bot-Machine to something which is no less annoying. Its not ready. There's hardly anything majorly new. Sure, it looks better. Sure, Fullscreen (which sucks for Spaces Users using CTRL <Insert Number>, since it takes the Fullscreen App to an alternate Window.....), sure, we get a few App re-vamps, but there's nothing truly new.
iTunes hasn't even received a single change, no new side-bar, nothing. This is not ready to go Live anytime soon. We're not even on a GM Candidate Build. There's a mile-long list of issues to fix, and Developers need to get their Apps sorted out still.
People have started base-less rumors that Lion will be launched at WWDC because they WANT it to be launched at WWDC. Its not ready to be launched at WWDC. I doubt they ever even planned to have it launched in time for WWDC.
At WWDC all that will happen is simple: We will get an iOS 5 Preview, and MAYBE, we'll get a few more incoming Lion Features Preview, along with a Release Date and Price Tag (unlikely). Most likely, they'll show off to the public the features that they're really not supposed to know about yet, seeing as the Lion Developer Preview is (technically) under NDA.
Its funny. They gladly slap a Teenager with a Lawsuit, but nothing on any of the various sites that are publishing Lion NDA Info. Not that I'm complaining.