SPy is a cool experiment which we should applaud, though perhaps it would be helpful to compare to ShedSkin, Nuitka, or maybe Numba along with Cython if the eventual goal is compile everything to Wasm.
I'd maybe quibble with "running natively on WebAssembly with speed in the same order of magnitude as Rust" given I expect that statement would be just as true if you replaced Rust on WebAssembly with the equivalent JavaScript.
But ultimately while I understand the motivation - at the beginning of my career before I discovered Python I wanted to write command line scripts in PHP because that was what I knew! - I think it is ultimately a dead end since by breaking from the Python ecosystem you end up having to compete against JavaScript which is not really that far from Python and has an existing library ecosystem to plug into.
I'd maybe quibble with "running natively on WebAssembly with speed in the same order of magnitude as Rust" given I expect that statement would be just as true if you replaced Rust on WebAssembly with the equivalent JavaScript.
But ultimately while I understand the motivation - at the beginning of my career before I discovered Python I wanted to write command line scripts in PHP because that was what I knew! - I think it is ultimately a dead end since by breaking from the Python ecosystem you end up having to compete against JavaScript which is not really that far from Python and has an existing library ecosystem to plug into.