The concept of trading in a car to "upgrade" involves combining the amount of equity you will lose in your present car when trading it in, with the increased amount you will owe on the new car. If that total larger debt is attractive to you; when compared to the advantages of driving the newer vehicle, the deal then becomes worthwhile.
Some people don't mind losing money on their present car, and going deeper into debt, in order to drive a newer vehicle. Other people would consider it unthinkable to do such a thing (particularly in the current uncertain economy). It both depends on the mechanical and cosmetic desirability of your present vehicle; on your economic condition, and on the perceived benefits of the newer vehcle.
Beauty (and feasibility), as they say, is in the eye of the beholder.