yeah i'm sure quite a few places might offer a trade in for the television. you are likely to lose your ass on it though. electronics do not hold value for very long at all.
you could make more on a craigslist sale then a trade in easily. however, nothing even remotely close to what you paid for it. after all, used is used and with electronics buying used equipment is a tricky situation.
i'd stick with the normal tv and ignore the 3d gimmick. or if you have lots of cash to blow go ahead and trade up. just realize that you would be lucky to get 50% on your old tv.