I don’t know where you saw that, but the original announce simply stated that SW update would be guaranteed for at least one year, and nowadays the purchase page says Software updates as long as device is supported
.
So as long as the kernel and phone specs permit it at reasonable costs, we should continue to receive updates.
Jolla has proven that switching is not a certainty after 3-5 years. The Xperia X was released almost 5 years ago, and the hardware is still better than a lot of current low/mid range phones.
It still feels so smooth that I don’t see any reason to switch and waste more resources honestly. Ok the only reason would be Android support, but 5G, 4GB and 64GB? What’s the need? Buy a SD card
(But I agree that there need to be more supported device for newcomers, or for us in a few years )