If it doesn't go through, what then? Do we see a return to people using special flags and having code to see if you are on an edge server or not? I sure as hell hope not. It would be groundhog day.
There's no suggestion that Microsoft will add this to Edge if it doesn't go through, is there? Hopefully, even if it did, it will do so progressively — designers have learnt to let go of pixel-perfect web styling by now, surely...
If we don't remember the past we are doomed to repeat it as they say.