I think BTC's price will go down slightly til the end of October and will rise up again on November. Just an opinion though.
I do not think so because fork means equal coins on both network. If the other network coin got value then it is more profit to those who hold it. This means there might be more demand before the hard fork since people wants greater profit . Then probably after the hardfork bitcoin will go down slightly before going up again to break its ATH.
Bitcoin value now is not fall down, because it was starting to raised up due to their current price now id around $4300 and I'm looking forward that before end of this month their value was meets up the $4500 or higher. Bitcoin value now in the market was in good condition and I think there's a lot of investors are invest again in this crypto currency, because as I heard banning ICO's in Chinese country will be deleted.