Without getting into want's vs needs vs buyers remorse, personal financials or why drive a new dually to work to get in your other dually to go to work, etc. Yes a 3rd Gen Mega dually will pull a couple short trips a year and the trip to grandmas house.
BUT, how many 10-12 year old super clean lowish miles 3rd Gen Mega Duallys are roaming around Manitoba for sale? And what do they cost? Not a whole bunch less than what you owe on the '15 I'm betting.
100k mile cherry shape 3rd Gen Mega dually is $30k US giver take.
What do they cost in looneys if you can find one that a snowbird has stashed away?