It seems definitely promising; it depends on how much adoption it's going to take. Even the most interesting languages (like Nim, for instance) struggle these days without corporate backing.
Worth pointing out maybe that MyPy is not a language but a type checker that works with regular Python. I've been getting into the habit of using it on everything I do lately and find it extremely useful. You can even do runtime checking on the types with tools like Enforce [1], and the Molten framework that was posted on here last week [2] uses MyPy typing as a core part of the framework.
[1] https://github.com/RussBaz/enforce [2] https://news.ycombinator.com/item?id=18107818