If this is accurate, I think it is really sad news. There are only four major browser engines left. If they give up development and switch to Chromium, it will be a significant step towards monoculture, which in the long term is bad (see: IE6).
It's not been officially announced yet, so the article could have misinterpreted rumours about replacing UWP apps with something like Electron/NW.js, or creating a secondary browser (like the Chromium-based Firefox Focus, which doesn't replace the real Firefox browser), or helping Google port Chromium to Windows on ARM, or something else involving Microsoft + Chromium which doesn't replace Edge. I hope it turns out to be something like that - modern Edge is a good browser.