Seems kinda strange to me to go from a 2011 to a 2013, for basically a tranny change. Car basically looks the same either color when you're driving
I could almost see going from a 2008 (old iDrive, maybe you've had it since new) to a 2012 last year. Then you could enjoy the 'newness' of the car and features, and have a '12 for 2-3 years until the F80/F82 comes out. 2011 to 2013 is basically the same car. And in the short term, '13 resale values are gonna drop like a rock when the F80 debuts. Remember how many people really wanted an E46 M3 right after the E9x M3 debuted? Not many. Sure, people will always want the "old" car, but resale values never keep up.
If I was the OP, I'd go test drive a 650i, M6, or maybe even a 991. If you're paying cash for a new M3, then an M6 or 991 shouldn't really be a stretch.
Life is short... drive some different cars