It's true to say prices have taken a pounding recently. I lost £9k on my '07 3.2 Mk2 TT after selling it a couple of months back.
Now that the prices have dropped I doubt they will go back up, especially as the Mk6 is on the way. Given the amount you will have lost on the purchase price you may as well keep the car, enjoy it and get the most for the money.
Blimey...between the two of us we've lost a shed load on TT's....how come you lost so much? Did you buy from new? What did you get for yours (if you don't mind me asking). When I was looking to get rid of my Mk1 TT 3.2, the one I wanted to originally get was a MkII 3.2 DSG and it was up for £24k on a dealer forecourt.
But hey...you know what...your never gonna make money on these kind of cars so I've just believe now that you pay the money, get your moneys worth out the car and then don't think about the depreciation, mods etc otherwise you'll always be grumpy.
I just think with the market the way it is, most of us should just stick with what we've got and enjoy it. We've made the expense so live with it...rather than selling, losing more money, and then buying a lesser car and always wishing we hadn't. Nothing worse imo as guys in family wagons, thrashing the nuts of them, cause they wish could have something different.