There is an alternative, in the event of disaster there’s room on board the Dragon capsule currently docked at the station for them to come back down. They’d be strapped into the cargo hold rather than a seat, but that’s acceptable in a disaster situation.
Don’t they need different space suits to board the Dragon capsule though? I thought I read something the other day saying they’d need to wait for Dragon-compatible suits to be brought up to them for that to be an option.
The suits aren’t technically needed for reentry, since the capsule isn’t supposed to be depressurized at any point during the trip. It’s just another layer of “if something goes wrong.” So if it’s a choice of taking that risk or staying on an exploding ISS you go with the risk. I expect that even if the suit can’t be connected to Dragon’s umbilicals it could still be sealed for at least a few minutes of air during the riskiest bits of the trip.
