Sure, nevertheless, having arrived in the FP2 era just before the FP3, I can assure you I don’t consider the FP2 as a stable phone, whatever FP might have said about it, whereas from what I have heard of it, the FP3 seems to be, although not always highly satisfactory, much better designed (i.e not having microphone/USB/reboots issues due to hardware). Software is an issue I agree, but I hope they do better with FP4.
FP2 sales went down already in 2017 and 2018, at the point that people thought Fairphone as a company was dead. The FP3 was needed then.
Would you rather pay a cheap 150€ phone every two years? Comes down about to the same price, but not the same environmental impact.
Honestly, I doubt it, as I said before very few people would buy the FP2 in 2019, because unfortunately not many buyers like you or me find the FP2 satisfactory enough still today, and if you don’t have any buyers, then your company remains a concept. And even by improving it, if there are hardware issues, then you’ll spend even more money buying spare parts and improvements.
Maybe the FP4 is good enough for this.