It appears that Sony’s Xperia Z1 is making it’s paces through the FCC filing system and suggests that it could be announced for US launch before September 30th.
The filing requests that the user manual, test setup photos, external photos and internal photos remain confidential until September 30th to insure that they have proper time to release it to the market. I understand that it has released in other markets at this point, but Sony has been mum on whether it will release in the US market.
The image of the marking tray on the device basically proves that it is the Xperia Z1.
The GSM bands also show that it is compatible with AT&T and T-Mobile, but sadly not with Verizon. This not saying that it will be on AT&T or T-Mobile, but given Sony’s track record it will most likely be a T-Mobile exclusive.