Regards the BTC price at the moment I assume that the price will fail back to 4300$ after the fork. I believe in bitcoin and I believe it will go up again after the fork, but for now it keep going down.
Another thought is the price goes down due to the amount of people selling their BTC since they don't wanna face the fork I am not sure if that has an effect, but I will not join the fork. I will sail after it
If one chain dies out quickly, the surviving chain will rise a lot. If not, the combined value will be lower.