I doubt it. Theyll push WWDC up (Or a WWDC Mac will happen earlier in the year). WWDC used to happen in early May anyway. Steve likes to use the codenames. He never said Snow Leopard was 10.6 either, just the seventh major release of Mac OS X.
As for whether its 10.7, its pretty clear:
"We took our best thinking from Mac OS X and brought it to the iPhone. Then we took our best thinking from the iPhone and brought it to iPad. And now were bringing it all back to the Mac with our
eighth major release of the worlds most advanced operating system.
1. 10.0 - Cheetah,
2. 10.1 - Puma
3. 10.2 - Jaguar
4. 10.3 - Panther
5. 10.4 - Tiger
6. 10.5 - Leopard
7. 10.6 - Snow Leopard
http://www.apple.com/macosx/lion/