The complexity of JS-based webapps is going to get higher, not lower. Only if that's the winning tradeoff. If, in fact, "ability to run well on a mobile device

The complexity of JS-based webapps is going to get higher, not lower. Only if that's the winning tradeoff. If, in fact, "ability to run well on a mobile device that is desperate to conserve battery power" turns out to be a more valuable trait in a particular segment of the market than "has lots and lots of complex JS logic that takes power to run" then software will evolve accordingly.