Agora has released the Web SDK 4.x. For details, see Introduction to the Web SDK 4.x. Agora will maintain the Web SDK 3.x, but may not be able to add all the new features in the 3.x due to structural differences. See the release notes of the 3.x.
To facilitate the development in various platforms and frameworks, the Agora community has extended the Agora SDK to a number of cross-platform frameworks.