Early in 2021, the Biden administraton deep-sixed the recently-completed "MCIT" breakthrough coverage regulation for Medicare. In 2021 and 2022, CMS began talking about its new plan, "TCET," transitional coverage for emerging technology. But it existing only as a term, or as a powerpoint deck.
On June 22, 2023, CMS announced the full proposed plan for TCET, with a notice & comment Federal Register publication. It's never been finalized, and its one-year anniversary as a "proposal" attracted zero attention.
Several bills still float around the Hill to restore more-or-less the automatic breakthrough coverage period offered by MCIT. The topic was mentioned during some 2024 hearings. See coverage at MedPage Today.
See a February 2024 letter from AdvaMed to CMS asking for quick action on TCET.