Next up on the roadmap, Typescript is working to add opt-in strict null and undefined checking which is probably the last area where Flow's type system is particularly better than Typescript's.
(It will be opt-in as Typescript follows a rule of increasing strictness via compile options to support the spectrum of JS needs, but also as it will not be entirely backward compatible with existing type definition files and will need some effort among typings authors.)
Thank you for correcting me.