Steam's end of service on Windows 7 and 8 is based on CEF, just as it was for XP and Vista. I don't see Google/Chromium dropping Windows 10 support at Microsoft's EOL especially given how much market share Win10 still has -- it would be shooting themselves in the foot.
In the meantime, instead of ditching Steam, ditch Windows. Steam works amazing on Linux, and with Proton, the vast majority of Windows games Just Work(TM). You don't even need SteamOS (although it helps).
I wish Valve actually spoke up against this EOL date, yet what they've done is just follow that date so far.