a lot of people think after the segwit2x activated the price of bitcoin will dropped to lowest down more than 30% or so from the current price , it is just a completely wild speculation .
Given the BTC/BTC2X futures at 0.2 BTC2X for 1 BTC, a price drop of 20% is logic. A drop of 30% is understandable, if we assume that bitcoin price is currently overrated.
Before Segwit2x is activated the Bitcoin can reach up to 8,000 USD then I think There will be a low drop about 6,600 USD - 7,000 USD at the end of segwit2x stage so Bitcoin can get a low correction and Altcoin prices will gain from this drop. First drop will be about 7,000 USD then we will see a deeper correction to 6,600 USD. However I believe that Bitcoin will recover again and it will continue to hit 10,000 USD in the early year of 2018.