For anyone who has the same concerns, here is a reply I received from one of the original contributors to the Calcite work, Eric Goforth who got a response from ESRI:
Got an official statement from Esri (specifically, Julie Powell who is the Product Manager for the ArcGIS API for JavaScript) on the status / future of Calcite. Her response is quoted in blue below:
This is a little bit of Github repo spaghetti, but I want to give you a little background…
As you know, Calcite has been around for some time and exists in several repos in varying states. The repo that you referenced, calcite-web, was the original Calcite implementation. Over the years Calcite has grown to include a full web component library, and the design has evolved over time. All new work goes into another repo, calcite-components, and our internal version of this is what the UI/UX of the new map viewer is based on. Calcite-components inherited everything that we needed from calcite-web. Now that Calcite is becoming an official offering, we are cleaning up all of the repos and references to Calcite, and will be publishing a new repo with the most up to date content. All other repos will be deprecated.
Here's the good news:
It is still the recognizable Calcite design that GEO Jobe knows, but has continued to evolve as design systems do. It includes many web components (not just css) that can be used directly in applications, framework-agnostic. It now has dedicated resources, so it will continue to grow.
It will be fully integrated into the Developer site, and simply licensed with our Essentials plan (or higher, and available for organizational users)
The source code will remain available for those that want to customize
We will be introducing our Design System story at the Developer Summit and EPC and the new repos will be available around that time.
So be on the lookout for the next iteration getting released around the EPC / Dev Summit 2021.
As expected, it won't visually depart from the current Calcite -- which means that any apps written with Calcite Web will still look Esri-authentic, even if they can't leverage all of the new features of the relaunch.
