OS X 10.7 Not To Be Seen Until WWDC 2011?

Lengthily discussing Apple's heroic focus on iPhone OS 4.0 for the past few month's, Daring Fireball says not to expect the next version of Apple's other operating system until at least 2011.
Gruber writes:
A few months ago, I heard suggestions that Apple had tentative plans to release a developer beta of Mac OS X 10.7 [...:]