If my math is right, Bitcoin Gold should debut tomorrow with a market cap of over $6 Billion, making it the #5 currency on Coinmarketcap, knocking Litecoin out of the top 5. From there, who knows. I could see it initially dumping pretty hard as it goes live.
With the recent pump of DASH, LTC's place in the top 5 is already pretty endangered. Personally i don't see the need for another bitcoin fork after bitcoin cash, bitcore,etc., but others seem to value bitcoin gold quite a bit.
Right now it's trading at over 0.05 BTC(BTG futures).
That means that market cap comes in at 5+ billion. I would expect an initial pump to take it over 7 billion, before a dump.