NXT will be making its debut on the USA Network on September 18th, but the entire show will not be aired on the USA Network for the first two weeks.
According to a report by PW Insider, the NXT episodes on September 18th and 25th will be two-hour shows. However, they will be shared by the WWE Network and the USA Network. The first hour will air on USA Network and the second hour will air on the WWE Network.
So from October 2nd onwards, NXT will be aired entirely on the USA Network, just in time for the Wednesday Night Wars.