Quoted:
I'm seriously thinking about a 2018 GT with the Performance Pack.  I had thought of getting a 2017 in the end of year sales, but the wait will be worth it.

The new 2018 engine configuration with direct inject + port injection and compression raised to 12:1 will result in a Mustang GT with 460HP & 420 Ft/Lbs of torque.
Add to that the GT-350's magnetic ride suspension plus the 2017 Performance Package features and you'll have a Mustang GT with 9/10ths of the performance of a 2017 GT-350.

Sounds like 2018 is going to be the Year of the Mustang.  There are already reports and videos of 5.0 Mustang GTs with the 10-speed automatic turning sub-4 second 0 to 60mph times.

And it will get better for Mustang fans.  Because waiting in the wings for mid-year release is the 720HP, twin turbo 5.0 powered GT-500.   With the new 10-speed automatic that thing should set 0 to 60 and quarter mile numbers nobody has dreamed that a showroom stock car could ever do.

Video:  2018 Mustang runs 3.8 second 0-60mph
https://www.youtube.com/watch?v=8JeAc_TnwnI

Video:  2018 Mustang release information
https://www.youtube.com/watch?v=kfIpsuCGhv8