BitGo employs the following criteria in choosing to support a fork:
A fork must be technically viable. Forks are announced and quickly users want to be able to support them. But, if the chain is under flux, undefined, or unsafe, BitGo will wait and be a trailing adopter of the chain.
A fork must have a market cap of at least $1B. There are many small chains out there, and BitGo is not in a position to support them all. BitGo generally supports chains which need security, and that usually comes with some level of market value.
A fork must have liquidity. If a chain is not supported such that the potential market value can be traded, then it isn’t a real chain.