Like Sparta I was pretty sure that Ford said a while ago that the the '15s would have irs. Regardless too bad they can't offer an optional solid rear to keep the drag race crowd happy.
It's not bashing. These are concerns that fellow members will have to deal with. These are the known problems with IRS. I also acknowledge there are major benefits of IRS.
What's more, if it's not going to be done correctly then don't do it. The current live axle is better on the Boss than the IRS in most of the cars out there.
One can only hope that if they go this route that it's because they intend to make it badass.