Popular projects like React use templates but require you to bundle the entire framework and the speed of the vDOM diffing happens at the speed of JS. What if it could take advantage of HTML templates to work at the speed of C++ by leveraging built-in browser support?
One of my hopes is that we can stop the bad trend of rewriting the same front-end components over and over again. Instead there could be a set of canonical components that people use for different web site types. If you're building an e-commerce checkout system, you could pull in the email address input built by Twitter, Stripe's credit card input, and the address input built by some person on GitHub that has 5,000 stars. Authors could leverage CSS properties and ShadowDOM for nice style hooks so developers could customize the branding.
The job of web frameworks could shift from "how do people build UI components" to "how do people build SPAs with routing, cookie auth, service worker caching, etc.". Not that current frameworks don't try to handle app level things but there is a lot more that could be done to make this easy for developers.
It would be nice to see web components as orthogonal to framework UI styling. We should be able to pull in web components from anywhere and frameworks should be smart enough to co-opt the components by treating them as native DOM elements (like div or span).
Sorry if this was sort of a rant I didn't have much time before work...