Actually I did get a 2019 MacBook Air and used it for about a week. (See my original post.) I thought the keyboard was horrible but decided that I would just live with it and try to get used to it. But if Apple is going to change the keyboard in the next year or so to something that I prefer, and something that's presumably more reliable, then the decision to return the laptop to Apple was a no-brainer...
That's actually what prompted me to buy the 2019 MacBook Air, I do have an older Air that runs out of RAM when I'm running XCode and Safari simultaneously. So I really need at least 8GB of RAM, and preferably 16GB if I really want to future-proof the laptop.
I only use my laptop when traveling. I have a big trip coming up next year so I need a new laptop before then. Hopefully Apple will have released new Airs with new keyboards by the time I leave. If not, there is an option that you haven't mentioned--buy a used ~2015 MacBook Pro. It will be a few percent bigger than a new Air in terms of footprint, and 30% heavier, which is a bummer, but on the other hand it will be super cheap and have a good keyboard.
That's how I justified the relatively expensive purchase price of a new Air with 256GB SSD, since my last Air has lasted me 6+ years so far.
(BTW, the current base-model Air retail price is $1100, not $900.)
On the other hand, the keyboard warranty for the butterfly keyboards is 4 years. That's great until it runs out. For many people that might not be an issue, but for me, looking at my current laptop which is now 6 years old, that's a concern. I understand that Apple has supposedly addressed the reliability problems with the latest 2019 revision of the butterfly keyboards, but they also said that about the 2nd revision of the butterfly keyboards and look where that got them. So please excuse me if I don't have good confidence in the latest revision...