I don't see it as THE harbinger, but one of many. Some people will use it for the same reasons that they obfuscate things today. See, for example, the dropbox client. It's python, but they go to great lengths to keep you from peeking behind the kimono.
I understand WASM isn't reverse engineering proof, but it certainly raises the bar. Especially sans source maps.
Source map is totally optional! It provides zero help in understanding asm.js or minified JS. I see what you're saying about binaries being opaque blobs, but I just don't see how that's different from asm.js or minified JS.
I understand source maps are optional...not getting the exclamation point. That's exactly my point, it's optional and therefore not much help.
Minified js isn't (so far) a barrier for me. Prettify and a short bit of debug clears things up. Chrome even helps[1]. I have not yet run into asm.js used for anything in my field.
I don't think it raises the bar at all. You could already do everything you can do in wasm today with Emscripten, and any harebrained attempts at DRM schemes shipped over the wire would almost certainly be using Emscripten. Wasm is easier to read than Emscripten'd code because of types.
I understand WASM isn't reverse engineering proof, but it certainly raises the bar. Especially sans source maps.