Maybe a less dramatic situation than your hand being removed, what if a bad guy figures out the ability to copy your palm print.
Then you would dispute the charge and have your own geolocation data or the store's video footage to substantiate your claim. This is a grocery store, not a diamond merchant.
If you happen to have attracted the attention of this master counterfeiter who has duplicated your palm you would simply have the option of not registering your new card with the system.
If this happens on a large scale, yes, the whole project is doomed.
If you find that someone has (somehow) managed to duplicate your palm print then you probably do not want to enroll with that option for payments in the future.
The issue is once your biometric data is compromised you have no recourse to regenerate it. Your solution is you just don't get to participate in these features anymore.
You're back in the same place you are already. If this putative palm print duplication technology becomes widely available then people will stop building technology that depends on palm prints.
As has been repeatedly pointed out, the risk lies with the merchants and the issuing banks (at least in the U.S.) for credit card payments.
EDIT: and, at least in the U.S. again, no-one is going to be able to force you to use this technology; there will always have to be an alternative mechanism because there are people with no hands, and a system that required them would be a massive ADA liability.