I was curious too, but I don't think that info has been put out there yet. The bolt pattern is probably the same, but offset should have changed do to IRS and new suspension.
I suspect that the wheel offset will be dictated more by the change to a double ball joint front suspension than by IRS. Think in terms of scrub radius.
Interesting question, I was actually wondering the same thing. Got some nice rims on my 13 GT and I kept the stock wheels. If they'll fit I'll throw the stock rims/tires back on and save these puppies for a 15 when I get one.