Mac OS X Snow Leopard (10.6) Possibly in Q1 2009?
From MacRumors:
"Apple's Director of Engineering of Unix Technologies Jordan Hubbard spoke at LISA '08 last week. This year's conference invited Apple's Jordan Hubbard to speak about the evolution of Mac OS X from large servers to embedded platforms". The presentation slides (PDF), besides generally interesting info on Mac OS X, feature a table that shows a release date of Q1 2009 for OS X 10.6 Leopard.