What will happen in
BTC bitcoin market when another fork hits bitcoin, results in emerging bitcoin gold as new coin
Will price of bitcoin go down
Will new coin get popularity like bch

No Bitcoin won't go down.
BGold uses a completely different POW algorithm, has replay protection and never claimed to be the real Bitcoin.
It's an altcoin. They said that numerous times now.For Bitcoin holders this is nice dividend.You either hold that Bgold tokens for future gains, sell parts of it or all for fiat or more BTC.
So it's up to you what you are going to do with it.
It will have no negative impact on BTC!!!