At this point TS is trying to keep runtime syntax in line with TC-39 (the language committee in charge of JS) proposals that reach Stage 3 (and thus likely to reach Stage 4 and general acceptance/use in the browser).

There is currently a Stage 1 proposal for a pattern matching syntax presented to TC-39. If it reaches Stage 3 then it is presumed likely Typescript will implement it.

https://github.com/tc39/proposal-pattern-matching