According to the Secrets of Paris newsletter:
On March 16, 2027, Roissy Charles de Gaulle Airport (Paris-CDG) will finally replace its confusing terminal naming system (T1, T2A, T2E, etc) with a simpler numbering system from 1 to 7. Boarding areas will be identified by letters rather than combinations of numbers and letters. Some airline tickets for flights after that date may already display the new terminal names.
The new terminal names coincide with the March 28th launch of the CDG Express, the non-stop train between the airport and Paris-Gare de l'Est station in just 20 minutes.
https://www.parisaeroport.fr/en/passengers/news/paris-cdg-terminals-change-their-names
https://www.parisaeroport.fr/en/passengers/transport-parking/public-transport-paris/cdgexpress/cdg