A quick check at microsoftstore.com shows that the 128 GB/i5 and 256 GB/i6 models are still promising launch date (6/20) ship dates, while the other models are already showing 8/31 shipping.

64GB/i3 $799 8/31
128GB/i5 $999 6/20
256GB/i5 $1,299 6/20
256GB/i7 $1,549 8/31
512GB/i7 $1,949 8/31

UPDATED:  As far as I can tell, those models were always showing an 8/31 ship date.