Core 2 Extreme will actually become the first Conroe processor to launch, followed immediately by Core 2 Duo E6700 -- as outlined by Intel's most recent desktop roadmap.
Intel is expected to ship the first desktop Core 2 Duo (Conroe) chips in July, 2006 and the notebook Core 2 Duos (Merom) in August, 2006. This means that we can probably expect Apple to ship the first Intel-based Mac towers some time after July with a Core 2 Duo in low end configurations and a Core 2 Duo Extreme in high-end configurations. The real question is: What are they going to call the new Intel desktop Mac?
All signs point to "Mac Pro."
What remains to be seen is what Apple does with the new notebook Core 2 Duo (Merom) chip. It looks like the new chip is destined to be the first upgrade to the current line of MacBook Pro notebooks.