The biggest hurdle to using TypeScript is the build step before it can actually be run. If the type annotation TC39 [0] comes to pass this would be largely taken care of; _hype_ waxes. (unfortunately the proposal has been stagnant for more than a year now)

A lot of the new frontend codebases involve a build step before running. For such codebases, TypeScript's build hurdle has already been overcome.

[0] https://github.com/tc39/proposal-type-annotations