What report shows the GTX380 launching in June?
semiaccurate.com which has been correct on everything about fermi up to this point is reporting it.
Also some others in forums are confirming it and they are more than just forum trolls. Do some poking around. gts 360 in late march perhaps early april (when volume actually starts to hit) and then June for gtx 380. They are hoping on revision B3 to give them much better yields on the part.
I'm not going to respond to the other part of your post because I do agree with it for the most part. But 5870s will not easily hit 1200 on the core. Pushing the voltage to 1.35(which is more than a slight boost), most cards will top out at anywhere from 1050-1075. The only way I cans see a 5870 hitting 1.2Ghz is if you're using sub-ambient cooling. Like the Phenom IIs, Cypress seems to respond better to lower temperatures than voltage.
I've seen 5870s at 1.2ghz using the stock cooler and this http://www.thermalright.com/new_a_page/product_page/vga/vrm/product_vga_cooler_vrm.html
Most spend time cooling the wrong thing.
A refresh will of course not only come with faster clocks but better board components that will incease the speeds at which they can clock