One thing that does stand out as being one of webasm's advantages: security. Since it runs binary/bytecode the browser's console window can no longer be abused to hack into a game's code that easily.
Is this correct?
Probably.
It's kind of hard to say for sure how it will be integrated into browsers.
There might be some exposed code, but the ability to manipulate it will most likely be limited.
You have to remember its just for browsers, so without knowing that it will have wrappers, it's kind of limited.
That is to say that if the current trend of pushing apps into browsers does not become more common.