In a number of ways, we're worse off now than we were 4 years ago in terms of price : performance ratio. Pretty much all because of parts prices, which have skyrocketed in the past couple of years. Neodymium is WAY more expensive today. Copper's more expensive, other metals are more expensive. Wood finishes are more expensive. Etc. etc.
Good speakers from 4 years ago are still good speakers. And the exact same speakers would likely cost more today than the MSRP they had 4 years ago. So you combine the lower MSRP and then lower the price even further due to them being cleared out, and they can be a terrific deal!
Now, obviously, they need to be in good working order. Good speakers should last for many many years, but the drivers are moving parts, so it's possible for things like the rubber or foam surround that goes around the driver to degrade or get worn from abuse. But other than that, it's not like speakers "wear out"
There've been some advances, particularly in the understanding and design of waveguides. But it's not as though every speaker out there is making use of the new developments. If the speakers you like happen to be a model from 4 years ago, there's no reason to avoid them