the halving is a non-event with respect to price, or at most it is an event of trivial proportion. There is nothing to price in or not price in.
The halving halves the supply of new coins from 3600 coins per day to 1800 coins per day.
If we take a simplistic view that there is a steady demand of 3600 coins per day at the current price then it is safe to assume that suddenly halving the supply while not changing the demand will cause an increase in price.
The problem with this is that everyone already knows that the supply is about to halve, and so some people will already have been acting upon that knowledge.
The halving does not halve the supply. The supply increases with every block. Bitcoins are not consumed. The 3600 or 1800 BTC mined yesterday will be part of the supply today, and the 3600 or 1800 BTC mined today will be part of the supply tomorrow, along with the 3600 or 1800 BTC mined yesterday. Even if you consider 50% of the coins each day as lost or otherwise consumed or unavailable, the supply still increases with every block.