That doesn't mean that the price can't increase... the thing is you wouldn't be buying BTC if there were a unlimited number of them wouldn't you. The block reward reduction is just the means to accomplish this. Of course there is less immediate inflation which could be argued that a price rises after the block reward reduction.... but saying prices rise currently because of said price rise as a speculative motor is just too far fetched.
This theory would only work if everyone already knew about bitcoin, and about the block reward halving. The way it works, though, is likely a lot more organic than that. As new people come in, they first find out about bitcoin, then about the block reward drop. That would push the price up.
I'm not saying this is the reason behind this particular rise. But the notion that all aspects of Bitcoin are already accounted for only works if everyone knows about them, and right now most people have no idea what a bitcoin is (though some may think it's the plot line of a Good Wife episode :-)