If bitcoin can actually help lower income types I don't think it's unreasonable that they might try to incorporate something in their financial services. Of course, bitcoin would have to be of real benefit to their customers and at the current time it isn't.
Well - if they wanted to, they could.
- Conduct a case study to see whether it was possible for them to introduce bitcoin as a payment option in their stores.
- To drive adaption, they could team up with providers of hardware wallets, or even introduce some kind of bitcoin cards (Neo Bee Cryprus comes to mind:
http://www.neo-bee.com/en/)
The motivation would be at least two fold:
* Less fees needed to be paid to VISA and other payment companies. This could run pretty high because of their sheer volumes.
* Avoidance of fraud. I'm sure some customers buy stuff with stolen cards, and WalMart's taking a loss on it.