With the caveat that this is not my area of expertise, at least in the U.S. the wild card here would seem to be Net Neutrality.
If enough of the ISPs slow-laned gaming traffic, that creates two possible paths for multiplayer fees. Either 1) by Steam directly needing to pay the fees to be white-listed into fast-lane traffic, or 2) Steam or some other service (Amazon/twitch, perhaps) seeing a new market to bring MP games under their umbrella offering fast-lane services directly to customers.
You can have 85ms latency for free - or 30ms latency for $9.99/mo!
So if you're just looking at the market of today, then I agree with the majority here that adding fees for this service would probably not fly in a decentralized market where no one controls the hardware, software, etc.
But change it up to where there's cartel control over the data exchange in select countries/markets, and that portion of the market at least potentially shifts.