Given that the Audi A3-etron has already been confirmed for the U.S. market, we know that its drivetrain will undergo the multi-million dollar process of U.S. federal approval.
With the A3 e-tron approved, my understanding is that it is significantly less expensive to than certify an already-approved drivetrain under a new model. So the VW Golf GTE should not cost VW too much to certify for the U.S. market. If VW is willing to roll the dice on a new Phaeton for the U.S., then surely the GTE should be brought over!
This reduced federalization cost is exactly how Audi is importing the Q3 SUV here as a last-minute competitor to the Mercedes GLA and BMW X1. Because the Q3 rides on the last-generation A3 platform, Audi federalized the Q3 model with the old 2.0T, for U.S. consumption, because that drivetrain and platform had already been approved for the 2009 Audi A3 2.0T hatch.