If they haven't support Bitcoin Cash, I'm pretty sure that they won't support all those new scam forks comming in the future.
After a long way of going back and forth, It was soon announced that they will support BCH. Apparently, the popular demand from users played a great part.
And as of now its implemented, Article here:
https://blog.bitgo.com/bch-availability-c252727ea1beSame question regarding the other forks that happened after Bitcoin Cash. Are they supported by BitGo?
For bitcoin gold, As of now they don't support it and I doubt that they will.
Bitcoin Gold is currently not supported by BitGo. We will continue to monitor the market viability of this blockchain to determine when and if we will support it. BitGo is committed to providing a secure wallet and takes great caution in adding new digital currencies.
As for the other forks or possible forks like super bitcoin, bitcoin god, bitcoin platinum etc.. There is no news about that but it should be given that they're a plain junk so they most likely won't support it.