It will affect bitcoin price, but if the segwit is successful the price will go rising again but if it is forking then we will see a downfall, but I am more optimistic, I think bitcoin will succeed so I will suggest you to buy now and hold
Why u think it will go down if there will be forking?
Lol people are worried now, after 1st august everything will be clear so price will go just up and up in my opinion