why do you think that the block reward halving will have this kind of effect on price?
We have the previous block halving to go by and we also have other alt coins to go by. People are invested in the network before halving and after halving they change nothing, so the price goes up since the supply is less.
Market prices incorporate information as soon as this information is available. The future supply of Bitcoin is completely transparent. All market participants are able to react now.
A price movement only happens when new information enters the market place. The halving is not new information and should therefore be reflected in the price already.