The "Who do we get that is better?" part would be the main reason to keep him. And that might be enough to save him in such a scenario.
But the "Why?" part: in this scenario, Arteta would have once again failed to finish the deal, and for familiar reasons: bad offense, players look exhausted despite the fact there are rotation options, etc. Has he actually improved as a manager season over season? In the fall, it always looks like it. But in the second half of the season the same cracks keep showing up.
Getting the team from where they were at the end of 2019 to where they are now is one thing, but going the next step is another job entirely, and in the scenario where this season ends in disaster, Arteta will have provided plenty of reason to question if he's capable of the last step. Something about the definition of insanity.
But it's the Kroenkes, so who knows? Arteta is basically Sean McVay without the championship, and I don't think McVay is going anywhere anytime soon.