Two points: they've already done it with the GT. From a pure performance perspective, one of the dumbest things they did was to forego an even better version of the Voodoo in favor of the Ecoboost for that car.That would be the dumbest move ever. The next hi-pop won't be doing that.
Secondly, it's Ford, and while they have had flashes of brilliance over the years, they don't have the best track record of keeping performance as Job 1. Winning the HP war probably isn't as important to them as promoting an engine program they've already invested hundreds of millions in. Hence, the Ecoboost GT.