Pre-orders will ship on the 31st, no sooner, according to Radio Shack (I called them, not a local store). Some Radio Shack stores are expecting to have some about the same time pre-orders arrive.
I think Radio Shack is the lead store, which would explain the June 10th for others (Target, Walmart and Best buy). Virgin often picks one store of them to be the lead store for roll outs.
On the 31st, you might also want to check Virgin and Boost stores (yes, there are some now). Call around to various stores, especially metro areas and outlaying areas (they often have fewer people rushing for them). Try and have them hold it before you drive, these seem to be going fast like the OV did.