To those who are still asking the same questions already answered, here you go:
Poly is giving us TWO YEARS more service before they shut it down.
No, this is not a Google decision. It is a simple End of Life decision by Poly. No, Google is not shutting down Google Voice. They've invested many millions of dollars in modernizing the service to support the paid, business-class version for Google Workspace customers, and the consumer version uses the same infrastructure. Google has also done a ton of work to modernize and convert the consumer side to the same back-end and the same mobile and desktop user interfaces.
People go ballistic every time Obihai/Poly announces the end of life of a product. There is absolutely no "but, but, I was guaranteed free phone service for life!" clause. Companies phase out products all the time.
No, there will not be any follow-on Analog Telephone Adapter (ATA) products that work with consumer Google Voice. As someone already pointed out, landline phone use is rapidly declining, and there is no money in making/selling/supporting landline ATAs.
The remaining market is in business IP phones that work with cloud-based or PBX SIP phone systems.
Your OBiTALK device does now, and still will support any SIP VoIP service provider that provides open SIP credentials. Free? No. Affordable? Yes.