The Debian Project continues to work on the unstable distribution (codenamed sid, after the evil and "unstable" kid next door from the Toy Story 1 who should never be let out into the world). Sid is the permanent name for the unstable distribution and is always 'Still In Development'. Most new or updated packages are uploaded into this distribution.
The testing release is intended to become the next stable release and is currently (as of July 2024) codenamed Trixie.