In this case it would be sell Bitcoin before the possible fork, then on August 1st it would be time to buy, when the fact is know.
I can imagine that that would be the right way to go too, sell now, let the market fall due to uncertainty, then buy back low and wait for it to rise after the uncertainty is over.
Maybe the market pumps after you sold your coins.Then corrects down to a higher low as before and you still have to buy back in on a higher price.
Just because your assumption seems logical to you doesn't mean it will happen that way.
Therefore I would be really cautious with selling now.
Bitcoin always tends to react pretty strange when many people think this or that has to happen at a certain point in time.