If Google doesn't drop Walmart eventually.
I was thinking quite the opposite.
There's no reason Walmart needs Google as a middle man besides their incompetence to build out their own service.
OTOH, Google doesn't sell goods (besides a few a electronic devices), they sell services, and getting Walmart to sign up was a home run for them.
They will have access to all the data....
I'm pretty sure all of that data will be sandboxed (unless they agree to share some operational data).
Walmart ain't that stupid, and they can be quite extreme in their measures. Walmart recently forced their 3rd party service providers to stop storing Walmart data on Amazon servers (AWS).