I would wait until at least next year and keep what you have for now. The 2016 is going to have a year to work out the kinks with the new style. Not to mention, Microsoft Sync will be gone to a new system soon.
Plus, you have no car payments!!!!! That's awesome! You don't have to have the latest and greatest to keep up with the Jones when you have a fully capable car right now that's paid off that hangs with the new model. (Sorry, but I feel bad for those guys with the pre-2011 models..)
2012 Mustang GT Premium
BLACK on BLACK 401A. A6, HIDs, Security, Rear Camera+Reverse Sensing, Remote Start, Comfort.
(Planning on CAI/Tune then I'll be good)