This presentation reports on a very recent development, following the May 2026 meeting, regarding ISO's initiative for the coding of language varieties. The outcome will directly affect the IETF language tag format (BCP 47), which is employed as the value of @xml:lang, @docLang, and similar attributes in TEI. The planned framework has been under preparation for years within an ISO working group, which has already produced the introductory standards ISO 21636-1, -2 (TR), and -3. Building on these, a coding standard—tentatively titled "21636-4" and intended to complement ISO 639 and BCP 47—is now being discussed in collaboration with the BCP 47 maintainers. The new framework will cover previously underrepresented aspects of language, including what are commonly called "dialects," with eight dimensions: space, time, social group, medium, situation, person, proficiency, and communicative functioning. These layers of description will enable powerful and fine-grained identification of language varieties across a wide spectrum of applications, from documentation and corpora to AI-assisted encoding. Thus far, consensus has been reached that the code will be implemented as a BCP 47 extension; however, the working group is still in urgent need of input from user and expert communities on a wide range of details, including structural design, identifier (subtag) format, and maintenance bodies. This poster presents the current standardization progress and the known roadmap, aiming to draw attention from the TEI and DH communities and invite future engagement.