Well a lot thing can happen in a year, but considering some more countries will legalize bitcoin i believe its possible to achieve 4000 dollars into one year if more countries does legalize bitcoin, if the same countries remains, well i would say 3000 dollars.
There is not much going on next year for Bitcoin itself and that should keep the daily changes under $100. There are many other coins that have big plans next year and that always boosts Bitcoin with a volume increase.
Face it, for most people, to buy another alt coin, they start with FIAT to Bitcoin and then forward, Bitcoin benefits from most new coins.