Kind of yes.
For simple browser as a general application platform you need a simple base technology where much can be shipped as library level. It would be fun to see WASM only browser with JS and CSS layouting solutions run as WASM compiled libraries.
So in theory WASM could be used as a first step to more simple browser but in practise it's propably just a fantasy.
Absolutley not. I love rust and would be happy to live in a world where I could write rust in any place where I would typically use typescript or babel or coffeescript back in the day, but none of that is going to be possible without an entire stack of tooling similar to that which already exists for the js-targeted ecosystem, and I have no problem with that, but people who ostensibly dislike "churn" claim to have a problem with new tooling and new solutions for building web pages and this is exactly the promise of wasm.
If anything, wasm represents the biggest shift in "churn" in the history of web development since it opens the door to dozens of new languages and frameworks that were previously impossible to use for web development.
But at the same time --
To all the people complaining that modern web browsers are too complicated for small teams to build and maintain, do you think WASM helped with that at all?
To all the people complaining that Javascript's lack of an extensive standard library makes it hard to quickly read/grok other people's code on Github, do you think that situation is going to get any better when people are using entirely separate languages to program the same webapps?
To all the people complaining that there are too many frameworks and tools being released for the web to keep up with, do you think that's going to get any better when suddenly every programmer and their dog can start porting any Open Source UI toolkit/framework to the web with low-cost DOM bindings?