There could never be a theft on the "Core" blockchain in the first place because the vast majority of the network is enforcing consensus rules that would see that theft as invalid. Violating those rules is a hard fork. Very very very few nodes on the network are left running software that would validate this miner fork. We're literally talking about dozens of listening nodes. The vast majority of the network will literally just ignore the fork because it's just an invalid chain like any other hard fork.

Your node doesn't pay attention to what Bitcoin Cash does, does it? Of course not! It's irrelevant to Bitcoin! The same thing applies here.

The "Core" chain would be unaffected (except for maybe some congestion from the attacking miners leaving the network, same as Bitcoin Cash) so there would never be any rollback required. Anyone who would have you believe the Bitcoin network would accept miners stealing Segwit outputs is trying to bamboozle you. This would never ever happen based on the node distribution we see today.

Meanwhile, the forking miners would need to pray that everyone installs software to remove Segwit. Who in their right mind would do that?

The whole scheme is at odds with the incentive design in Bitcoin. Ask around. Nobody is going to adopt a hard fork where the miners steal all the Segwit outputs from users. They'll just keep running Core like the vast, vast majority of the network already does, and everything will remain as normal. Don't be bamboozled by these frauds fooling you into thinking this attack could work. They are feeding you misinformation completely at odd with how network consensus works. Anyone with a basic technical understanding of Bitcoin's consensus rules and node distribution understands this.

At most, if you have some coins in 1xxxx addresses you might get some airdrop coins on the hard fork chain that you can sell. Chances are they will have no value, but anything is possible!!