The real problem with check-cashing places are payday loans. Low-cost checking accounts from Walmart won't stop those.
Alternatively, it might be good to seek out a service that you can offer that would be a complement to what you expect the Walmart service to evolve into. I don't know what that complement would look like... but I do sense that it is likely pretty profitable.
In any case, the WORST thing they could do is sit still and assume business as usual. I mean, there is clearly a train coming...
it's time to get out of the way.