My theory is that the block being halved creates a bubble-- it will drastically increase the price since miners will do one of three things
1) Sell their coins at a profit, if they are getting half as many bitcoins per block, over time they would be likely to charge at least twice as much.
2) Hold their bitcoins that they've mined. Holding them will also increase the price, as there are less coins being traded.
3) Stop mining.
The third would only happen if the electricity costs outweighed their profits which leads to my question--
Are miners currently a large enough portion of people selling bitcoins to significantly impact their price?
If the miners are a large enough portion of people selling coins, they would raise the price to remain profitable.
Whether miners sell or hold, the price should increase (assuming we continue to have increased adoption) when a block is halved. Once the price raises to a value that is considered "unreasonable" to bitcoin users who aren't mining, the price should drop to a more fair value.
This is all just speculation, and we really won't have "good" statistics for it until we get to see the next halving, but let me know what you all think.
Chino