Could try and snag a deal on boxing day, but really, in general it's pretty tough to predict what any tv will sell for weeks or months down the line.
In my personal opinion the best time to buy a TV, is when you want a new TV. There's always a good TV on sale, because a company like Best Buy always wants to sell you a great new TV. I wouldn't deny myself while waiting for a magic window of opportunity that may or may not come. Flat screen technology has balanced out and the prices have leveled probably to around where they will remain. Prices may drop now and then, but usually as it coincides with technology improving. Sales will come and go and it may always seem like the next deal is the best one, but really, I see a good sale every week.
Don't worry about what time of year it is or what might be coming down the pipe... find a deal you like at the price point you want to spend and start enjoying 
