Something which I think could be helpful for the overall ecosystem, and allow both type systems to coexist and thrive, would be more attention put into tools which transpile code and type definitions between the two languages. The two most popular projects that I could find[1][2] are unfortunately incomplete and have not received any real updates in months.
[1] https://github.com/joarwilk/flowgen [2] https://github.com/bcherny/flow-to-typescript