Indeed Apple has made a tremendous commitment to incorporating the Java Framework in to Mac OS X. And I know from my discussions with them that they are very, very, excited about the prospects of Mac OS X becoming a primary Java development platform.
That being said, my impression is there's lots of excitment around Objective-C too. And I don't see it becoming an "either - or" situation any time soon.
I think one of the reasons that I'm so interested in Mac OS X is that there's Java, Objective-C, and Unix ... all in one beautiful install.