It depends on what you define as relevant. I'm assuming you mean something like "worth buying" and there are plenty of older IEMs that are still very much worth considering or even greater value to purchase nowadays.
Etymotic's ER series, I imagine the Blessing 2 will still be relevant in a couple years given that the Blessing 3 came out and is mostly sidegrade. The IER-M9 came out around the same time as the Z1R, the Andromeda (love it or hate it) was revised in 2020 but it has remained relatively relevant since it first came out, the Drop + JVC HA-FDX1 is close to 5 years and still relevant. The Sony MDR-EX1000 still offers some of the most resolution per dollar you can buy (though at the cost of siblance).
While I have been guilty of doing it myself in the past, I think that in general it's a bad idea to make generalized statements.
Not every newer earphone is an upgrade compared to its precedessors, look at the Blessing 3 or what Sony released to follow-up on the EX1000 and EX800. They were nice earphones but they didn't bring the technical improvements that many wished or hoped for. Even if Sony releases a Z2R soon, the Z1R will be anything but irrelevant, it will still be one of the best DD IEMs on the market.