Browsers have said that they are unwilling to ship any new cancelation mechanisms given that AbortSignal already exists, so we can't ship a different CancelToken. But I think there's a path to standardizing a subset of the existing AbortSignal machinery [1].
(I am on TC39 and while this isn't my highest priority I did bring the topic for discussion at the last meeting [2], and there was support from the rest of committee.)
[1] https://github.com/tc39/proposal-concurrency-control/issues/...