Depends on what they announce at WWDC, if they are using the new Intel chip, then they have to wait for Intel to be done with it, and that looks like fall.
But they could announce a release as early as say...a few weeks from the conference.
If you get a Mac now, it's not going to be obsolete by any means for years to come, even if they release an update in fall. I'm still running Tiger because I don't want to pay for the update right now, and because I think 10.4 is more stable at this point, and doesn't run as many background processes, which means it'll run quicker.
By the way...it's already summer.
"Nothing is impossible. You are only limited by fear and even that you can overcome."