I will hit 3 MM before the end of this year. I expect the same treatment I got when I hit 1 MM and 2 MM...nothing! I appreciate occasionally being recognized for my loyalty to DL for being a MMer but beyond that I have no expectations for DL doing anything special. I suppose I'll get a new DM card that will have 3 MM rather than 2 MM stamped on it.
I agree with others that it would be very nice for DL to recognize those of us that didn't just hit DM one year and left for another airline but rather made a long term commitment both time and financial to their airline. Some extra Global UG coupons or a bit of a bump on the UG list would be wonderful. Hopefully someone at DL is listening and monitoring this discussion!