Between that and someone actually creating a viable Steam competitor, I will say the government breaking them up and rolling out their own solution would be even less likely. You'd have fights on both sides of the isle and from privacy groups. Not that we have much privacy now under the current scheme, but there's at least a tiny bit of separation between V/MC and the government.
What should happen instead is regulation. They should be held to the same standards as legal tender since they're used in place as such. They shouldn't get to decide how it's used, and that should be enforced.