I've read that somewhere as well, a Coyote based V8 in the new Ford GT at some point.  They are saying 600+ HP with the Ecoboost in the GT, nothing specific yet, but they are saying the hp/weight ratio will be the best for any production US made car, and possibly the world, right now.  I'm unsure how much more a Coyote based v8 would weight compared to the Ecoboost v6.  Say the boosted V6 will be 650hp or so, but the V8 will weigh 80+lbs more, but give another 165 bhp - might be a good trade, who knows.  If you like V8s over boosted v6s it would be for certain.
As much as I like these new models (3) that they've come out with from their performance shop, I'm still really interested in the ecoboost Mustang.  Since the mid 80s there hasn't been a turbo4 Mustang, and it was one of my first cars back then, so I've always had a thing for them.  In the next few years there will be some great mods, already are in fact, for this car.  C and D magazine got it into the 13s, and 5.2 0-60, but its flat handling and braking was the big part of their story.
Also, if anyone is on Face Book, Direct Speed's site has a bit of video of the new Ford GT running from behind, fantastic sound.   
https://www.facebook.com/districtspeedfans?fref=photo