
I'm not worried YET.
A long time ago I had a 440-6pack Cuda', 4-spd. I loved the "Big Block" torque that car had.
When I got the new SS Camaro I was pleasantly supprised that the 376 C.I. LS3 felt like it out pulled the Cuda' that I used to have (by a lot!).
What will "make or break" the new Stang' in my opinion is it's torque curve and output. It's hard to get both HP and torque out of a smaller engine.
At this point we are all guessing. But I do expect the new version of the Mustang to be impressive.