Why would they? They offer same day to two day prime shipping so unless they want to start warehousing every prime item at WF, that doesn't sound logical.
I'm sure they'll put amazon lockers outside but to turn WF into products hubs for their online business doesn't sound feasible. Why would the customer order something to ship to store in the same time frame or less they could ship to their home ?
I don't think it's about lockers either. Call me crazy, but when they buy a grocery store chain, I tend to think it's because they want to sell food.
Instacart, Blue Apron, Hello Fresh, Amazon Fresh, even Uber is getting into food delivery. It's a huge market that isn't going away. This puts Amazon closer to being able to deal with the last mile cost problem than any of their food delivery competitors.
Now long term who really knows how much this could help their non-food business. I don't know the logistics of the grocery store industry, but I'm pretty sure this isn't just a purchase of the stores consumers visit. I'd imagine Whole Foods already has a delivery and warehousing network set up to supply its stores that Amazon could utilize, and grow, for other things in the future.