This is what I think we'll see. The 3.7L V6 we know today will be the base engine. For a couple thousand bucks you can upgrade to a 2.5L EcoBoost. The draw of the EB I-4 is better fuel economy and that cool "EcoBoost" badge. Think about a psuedo-hybrid Mustang that can manage 35+ MPG on the freeway but still be fun to drive with killer low end torque. The threats of $5-6/gal fuel prices would help it sell. The 5.0L will be the standard GT engine. There will be an optional 5.0L Boss engine upgrade for $2-3k. This would also come adorned with a special GT or 5.0 badge to let people know it has the Boss engine upgrade without being a blatant copy. It would still lack the other Boss components so that the Boss 302 owners don't feel jipped. I'd love to see all 4. I know a lot of people will disagree with this but I'm going to bookmark my post and repost in 2 years to see if I'm the next Nostradamus

 

Hmmm... would be neat to be able to click off an option box and get all the Boss stuff on a standard GT sans the Boss appearence going forward, maybe call it the Track Pack again to differentiate it from the Brembo Package.