I wouldn't mind a nice retrace back to 16k or so by January 1st. After that it can go full bullmode and blast those targets. Saves me some in taxes 
Blowing the current price below 17K USD next year will surely create havoc on BTC community. It just mean that Bulls are weakening and might be a dejavu on the last bull run. I'm hoping that BTC will above 20k USD next to start a fresh uptrend. Holding the 20K USD mark will mak traders confidence to acquire more and it's a confirmation price that a new uptrend form.
It may happen as people tend to sell at the end of the year, a retraction below $17k won't be havoc, just a normal thing in the market. Bitcoin movement seems going sideways in the last week, fluctuating within $18k-$19k but can't break the resistance, if it last for 2-3 weeks people may consider to sell rather than hold.