Not a Mill spokesperson but figured I’d chime in.
Last I looked the sandboxing for WASM relied on you being restricted to a 4GB address space, which means most heavy duty server applications are out. When 64-bit WASM arrives it will likely involve slower code that has to perform runtime checks to enforce the sandboxing.
Also the power efficiency gains are the whole point of the Mill! This is the arbitrage Ivan mentions in his talks figuring out how to get the generality of an x86 CPU but with DSP like performance.
Cerebras is not really comparable because they are throwing out the window one of the main advantages of the Mill. The Mill only requires you to recompile your existing C/C++ code. Cerebras and GPUs require requiring it, and they require that the particular computation your software is doing is the kind that is massively parallel. Most day to day applications most people use for their work and that are running the world servers are don’t resemble the kind of workloads that GPU/Cerebras are good at.