Right, they will never stop, there will never be a ceiling at which any browser vendor says "okay this is good, let's just stabilize at this point and refine what we have". There will always be the endless thirst for greater abstraction, deeper access to host hardware/peripherals and I/O, and really just more ways to turn the web into a profitable software-delivery mechanism.
What's wrong with that? It's not like it's ever going to go back to a "web document" only delivery mechanism, so might as well make it very very good at doing what it is already used for
