Bitcoin Gold and Bitcoin Cash are not serious threats for Bitcoin and I don't believe they will have any significant effect on the long term on the echo-system. However, forks have the advantage of forcing open debates around serious issues.
BCH prices will vary and fluctuate independently or separately from BTC prices. For example, BTC 1.0 could be worth $ 2500 and BCH 1.0 is worth $ 500.
Bitcoin remains no 1 and will not get shifted
