The discussion of shader language had been very contentious. As of very recently there is a proposal for a textual language that is semantically equivalent to SPIR-V, and there seems to be agreement that this is the path forward. The submitted link is a presentation with the proposal.
It’s best understood in the context of the Minutes for GPU Web meeting 2020-02-12 Redmond F2F, which also has some discussion about design choices - how much syntax sugar, whether types should be explicit, inferred, or optional, etc.
The previous proposals were some profile of SPIR-V, a binary format, and Apple’s Web High Level Shading Language proposal, which evolved into Web Shading Language. Both of these had disadvantages that made them unacceptable to various people. It’s not possible to use SPIR-V directly, largely because it has undefined behavior and other unsafe stuff. The Google and Mozilla implementations addressed this by doing a rewrite pass. Conversely, Apple’s proposal met with considerable resistance because it didn’t deal with the diversity of GPU hardware in the field. There’s a lot of ecosystem work centered around Vulkan and SPIR-V, and leveraging that will help WebGPU considerably.
(The above is somewhat adapted from my recent blog post with GPU compute resources, but the new shader language is definitely the interesting news).