do yourself a favor and run the numbers, just make sure you include everything you can think of. I was thinking about trading my 2010 Rubi I bought used in on a new JK in a year or so (have other bills/priorities first) because I was thinking about things like full doors, hard top, better radio, uconnect (or basic bluetooth connectivity) or maybe go to a 4 door.
Here is the cost I came up with to trade after owning mine 2 years (for about a $25K JK):
new sales tax: $2187.5
new down (assuming I am at break even point): $3000 - this should get me to the same amount financed.
restarting finance charges: $6905.97. High interest rate due to a previous divorce
Total: $12093.47 more if I trade (again mainly due to new interest charges).
So in my scenario, I can pay retail for the items I want and still be less than half the overall cost to trade in. I still will not have the new motor, I will not have a new warranty, or the new interior, but I can have both tops, both OEM door styles (even paying $1K each for doors) either an RBZ AND UCONNECT or a better aftermarket unit, keep my underseat carry boxxes, and still have a Rubi over a Sport.
You may want to think about how much in interest you will be paying over what you have now. I hate throwing away money on gas, but I hate throwing it at a company for starting over again as well.