It’s effectively already there, it’s kind of what the Audio Entrypoint Extension does already except routed into Roon via this new (…well 2 year old now) API (node-roon-api-audioinput) so that the stream pops up in Roon as an audio source with a custom icon, rather than a pseudo-radio station.
So in theory if you wanted to code something today you could, the code is there in Roon, you just need to send a stream to it. Although I expect Roon are planning to work with vendors to build / certify this into hardware devices with ADC capabilities ala Roon Ready (but for inputs, rather than outputs) with nice icons and maybe the ability to switch input sources in Roon.
In short, I expect this is more than just vapourware, as most of the code is already there in Roon to handle this functionality.