How long do you think Binance will hold out for before making it mandatory? I don't think they will for long.
Binance fled to Malta not that long ago, and for the time being they are safe in my book. The only thing I expect them to do in the near future is to start rejecting US citizens in an attempt to shake off the US authorities.
Some of the largest exchanges have already been doing so for quite a while now, and it's the safest possible move because of how active the US authorities have been and will be getting in the coming years.
I hope that whenever Binance decides to do anything that would require them to terminate user accounts, that they give them enough time to withdraw their funds without subjecting them to ridiculous verification steps.
If Coinbase allows people to withdraw their funds without any hassle prior to their account termination, other exchanges should be able to do the same.