I am also pretty sure with that since many people will sell their bitcoin gold for bitcoins we can expect that the price of bitcoin will go down for a little and we must use that opportunity to buy more bitcoins
Define "a little". Will "a little" be more or less the value of a BTG?
And really, it's funny how everyone here agrees that the BTC will fall. Whether it's a little or not, you can make money out of a fall. And that's why I think it won't just fall a little. It will fall
-a little before the BTG because of those (like me) who prefer to keep things safe & cash on the artificial rise
-then right after the BTG because of those who had bought BTC's just for the free money (those won't buy BTC back), and everyone who predicted the dip & sell to buy back later
-then from the panic effect
Of course it will rise back, in a few weeks or months, I don't doubt that. Just consider what will make you win the most: betting on the dip or on the BTG. But you can't have both, only a few quick/lucky people will.
Of course you also have to combine with altcoins that will be fed back from the BTC after the fork, but I don't know if it's the same ones that will rise back. Perhaps one (eth?) will more than others.
(edit: is the dip starting right now as I'm writing? Looks like it)