I think price of bitcoin will drop because people will go back from BTC to alts. Most of people just want to earn more BTC with this fork.
Drop on bitcoin's price just after the fork is quite sure but this drop might not be quite big as speculation for bitcoin gold is not that high and people are buying bitcoin not only to get forked coin after hardfork.
bitcoin price will drop only if you think the current rise was because of this fork! but i really don't think this fork had much to do with bitcoin price rise. because nobodyeven knew about bitcoin gold fork when the rise started and when ATH was near so little were aware of it.
and this fork is not really taken seriously anyways!
I knew about this fork before alts started going down this much and I menage to sell some alts so I can buy them 1-2 days before fork so I can have more of them. I do think that main reason for BTC to go this much up is because of the fork and we still have 8 days until fork happens. I think BTC will go to 6000+ before fork, but that is just my opinion. We will see what will happen.