If you go to
www.blueoval.com, they already have alot of the engines planned for the mustang probably in development or at least testing and since this will be based on the thunderbird chassis it will definately have room for at least a small V8 and rear wheel drive, which is good. I seriously doubt any speculation that it will have a 4 cylinder because many companies tried that in the 80's and it failed horribly, not only that but any mustang fan would complain and i'm sure ford isn't that stupid.
Whatever the styling is, i'm sure the next mustang will handle better, get better emissions and fuel economy, have equal if not better brakes and will have pretty good power.
I've heard that the 3.8L is going bye-bye and that in it's place a 4.0L V-something engine will be offered (don't know whether it's a V6 or V8 but it's supposed to have over 200hp according to Blue oval news).
I'm excited to see what the new mustang will be like, but i will miss the "fox" mustangs that have been around for so long.