IMO the probability of it happening is about 50%. Considering the btc pump happening right now because of some factors, it is not impossible that a dump will happen soon. It is not also impossible that the price will continue to rise months from now so the probability of bitcoin reaching 1000$ each in 2016 is about 50%.
A couple of good days is all we need. With halving around the corner, we may even reach $1000 in July.
I would put the probability at over 50%