AMD promises to shoehorn support for Zen 3 on older motherboards...but doesn't know exactly how yet...and assures us Zen 3 will definitely be the end of the line for older chipsets. Also, I've been tinkering with my 3900X overclocking :)
Article
https://www.anandtech.com/show/15807/amd-to-support-zen-3-and-ryzen-4000-cpus-on-b450-and-x470-motherboardsContact and more :)
https://www.geektherapyradio.com/