Wizards will never remove companion as a mechanic. The argument that other card types are banned like that is nonsensical since the card types banned are clearly not meant for constructed play. This is way different and there is no way they'll remove that as a mechanic. Suggesting this is similar to suggesting they'd ban all Delve or Phyrexian mana cards instead of Dig/Cruise and Probe/Misstep. It won't happen.
They also won't errata how companions work. This is also something they haven't done in a long time and would open a lot of phylosophical questions about the game. You wouldn't even want that because that would mean they're willing to errata cards for power level reasons instead of banning them, an approach only online-centered card games take (nerfing), which would be terrible for Magic.
I also don't see any problem whatsoever with banning the card. It has been discussed before (I clearly remember this being the case for Yawg Will circa 2006, with Menendian advocating for it constantly) and this would be clearly an exception to the rule since a restriction wouldn't solve the problem. It's bad, I agree, but it's the only solution possible. They'll probably wait a while before doing this, to see if the meta adapts. I'm just sad that there's a high chance Narset got restricted for no reason.