I've cooked many things that have been in the freezer for almost that long (actually, I did once do a 2-year old bird). There are two keys to having it taste OK (it will certainly be safe to eat, so you don't need to worry about that):
1. The freezer must not have been allowed to get too warm. The colder the freezer, and the less it warms up during defrost cycles, the better. However, if you have eaten ice cream from this freezer and that ice cream sometimes comes out really soft, then your turkey may be a little "off."
2. The turkey must have been packaged really well. Ideally, it should have been in some sort of vac-pac, but for a big bird that is difficult to do. If I were going to freeze a turkey for a really long time, I'd spatchcock it first and then freeze it because that would let me easily put each piece into a Foodsaver vacuum bag.
Finally, for a holiday meal pretty much everyone recommends getting a fresh turkey, or at least get one that was slaughtered fairly recently. It's a big, important meal, so why serve anything other than the best?