Of course I don't know, But it stands to reason that if supply remains constant and the block reward is halved the price should approximately double.
If people are set on buying X dollars worth of coins every day regardless of dollar price then a double makes sense (with some other probably false assumptions). But if people want X coins it all depends on their elasticity of demand and it could be a much bigger increase. I think the first is much closer to the truth, but I think that in addition to a supply decrease we'll experience a demand increase over the next year (and the next and next and next...).