It's a bad financial move to trade in a car that you're upside down on. It'll make your payments higher and you won't qualify for as good of an interest rate and you'll really be stuck with that next car. If you go for it, prepare to own it for a very, very long time.
Keep your current car for a little longer and pay more than your regular payment to get back in the black on that loan. Once you've got a little equity, go ahead and trade it in or better yet, sell it on your own.