Both the refurbished FP3 and the refurbished FP3+ are currently marked as “Temporarily out of stock”. They might become available in limited quantities again, but if my memory is right, the (new, un-refurbished) FP3+ was also marked that way until it has now been marked as discontinued.
The FP1 was delivered over a period of 15 months (from the very end of the year 2013 to March or April 2015), the FP2 a total of 39 months, and this indirect announcement now makes the span for the FP3 and FP3+ combined around 40 months.
I don’t think that’s a necessary consequence. The FP3 launched in September 2019 after a break of several months without any Fairphone availability (new FP2s were discontinued – I think – at the end of March 2019, and a few last refurbished FP2 were sold in July or August 2019). The period from the launch of the FP4 (autumn/winter 2021) to the discontinuation of the FP3+ now was actually the first time two Fairphone generations were available concurrently.