2011 was a mid-cycle refresh, not a redesign.
OP, there are plenty of "2014 or 2015?" threads around here. You're likely to save $8K or so getting a '14 now but your post doesn't suggest that that's a big deal to you. If you're worried about waiting (probably until this fall) for a new car, you can always buy something cheap, ragged and mechanically robust off CL. Think $4K Chevy Malibu or something, you might even get your money back out of it when you resell.
The 2015 GT won't be any faster than the current one. Same engine, heavier car. Direct injection is coming for the Coyote but not this year.
De gustibus non es disputandum.
Well then, forget everything I said.