Very true and so very close to what I think is Microsoft's true motivation: Office. Viewed through the prism that Office is Microsoft's cash cow and the criticism that the Office version available online in browser is limited, like Google Docs is limited (there's at least one feature that doesn't work given a large enough set of features from Word...), asm.js makes perfect sense.

Perhaps Microsoft will tier their products in a different way. A Office 360 subscription (or whatever it is branded) will get you access to Office, running in a browser, under asm.js. Perhaps they'll do something different. Sooner or layer, however, the Microsoft embrace of this technology will be monetized.

There are side-effects. Microsoft can sell tools that now run a tranpiler to put executables on the web. They might or might not use LLVM to that end.

This development means that asm.js has become a defacto standard. It is too soon to tell if this will be more widely adopted, as defacto standards fail al the time. I think, however, that this one will stand. Quite likely we all are now going to be freed and constrained by small design decisions made long before this adoption came to pass.