Not happening. ANT Pool has a huge investment in Bitcoin Cash and would swoop in with mining power to protect their investment.
The 51% attack is carried in secret. Noone has any way to know if it is happening until the longer chain is published. And after that, it's too late already. Someone could try to catch up with (not anymore secret) longest chain, but the damage has been done - the state of the network has already changed. Actually switching it back is only adding salt to the wound. Noone would trust that coin again anyway, and it is worthless to try to rescue it.
AntPool is busy mining Bitcoin, because it pays better:
so it can't constantly police BCash chain by over-provisioning it.