If you have 10000$. It's better to buy ethereum. 2018 is the year of ethereum

Buying bitcoin next year wont give you alot of profit. It might increase in value but not twice its base.
Best of luck
Well, it is depending what kind of holding you are. If you want high profit try to join ico project. Doing a research before joining is necessary. Join ico project can make you 10x or more profit. But ico is involved high risk risk too.