It's not as decorated as some of the other resorts (and decorations in general have diminished across Disney, although in my opinion I don't notice it much).
It is decorated however, and you definitely will be in the Christmas spirit when you're at the Fort!
Oh, and by the way, the Fort doesn't really need to decorate if they didn't want to. The amount of decorations that you will notice at the campsites will be more than you probably can imagine. Some of the displays that people showcase put the resort decorations to shame. Take one night and walk/cart/bike around some of the loops, if that doesn't put you in the Christmas spirit, I don't know what will.
I'm not joking, it's like a big winter wonderland, people go ALL OUT decorating their sites for Christmas.