ussualy bitcoin price in year, before christmast until end year bitcoin price down
you can see in 24 december 2015 bitcoin price in 460 dollar and then down , until price 410 dollar in 27 december 2015
so in christmast and new year much people can sell bitcoin, to get holyday, christmast and new year holyday
if much people selling so bitcoin price can down
The price can fluctuate a little, but I don't think Christmas will have an incidence on the price. I think on the contrary the price will stay stable and will continue to claim to reach the 800USD in January.
The best is to wait and see after Christmas, always hard to predict the future