That's not the trend that we're observing. As much as publishers and developers want to control their sales channels, the current trend is for them to move towards Steam, not away from it.

The more likely outcome is that developers would segment matchmaking into people with kernel-level anti-cheat, and people without it. This seems fair to me.

Several big publishers did move away from Steam until Valve conceded some of their revenue, reducing their cut from 30% to 25/20% at certain revenue thresholds. That convinced the publishers to return to Steam, but it showed that Valve isn't immune to being flexed on by the bigger players.