Unfortunately, Apple will only replace the butterfly keyboard for 4 years after initial retail purchase of the laptop.
I dread the eventual breakdown of the new butterfly keyboard after the end of February next year, when I'm on my own. I hope iFixIt will start selling DIY repair kits, or the cost to repair at Apple makes such a frequent failure a non-starter (in which case I'll turn it into a fixed-place computer in the house, with an external keyboard).
I wouldn't be surprised if Apple bended that 4 year rule, though. But also realize that Apple will eventually stop repairing all computers just due to time passage. And also, eventually, from a financial perspective it's more cost effective to find a working used computer (after heavy depreciation) than to actually do a repair even if that repair is doable.
I do think that their replacement keyboards have better reliability than the early models. I didn't have any problems after getting mine replaced - I believe I used the replacement keyboard for around two years. But I still wasn't willing to keep the computer longer. I went straight from the 2016 to the 2019 16-inch MacBook Pro.
In any event, it was a nice opportunity for an upgrade. My 2016 was still worth $1000, and I ended up with 4 more cores, double the storage, and an absolutely massive increase in graphics performance. Using the education store and picking up in a state with no sales tax did a lot to make that price more palatable.
1. Get your keyboard repaired (free, I assume)
2. Sell that thing online
3. Get this one.
I mean, this has a quad-core option, too. It's a no-brainer better machine.
I have the 16-inch that has the same keyboard mechanism as this. It's 100% an evolution on the previous design. While it is early, it's a proven design and there's no chance of it having any of the issues that the butterfly keyboard did.
I feel like my 16-inch is the computer I intended to buy in 2016.
If you can afford the upgrade cost after you sell your current one, you won't regret it.