As you may have read in this blog post, we plan to deprecate TSLint in 2019 and support the migration to ESLint as the standard linter for both TypeScript & JavaScript. This will not be an immediate deprecation; on the contrary, there is a lot of work to do to ensure a smooth transition to the new tooling without any regressions. There are features, test suites, and conveniences in TSLint which we hope to retain in the migration. There may be a period of time when there is overlap between the two tools and TSLint early adopters are recommended to run both linters to ensure full code check coverage (to a reasonable degree such that performance doesn't suffer drastically).

I will be closing some feature requests in this repo which now feel out of scope because we expect them to be handled in the ESLint / typescript-eslint roadmap. One example of a category of rules for which new feature requests are most likely to be closed / rejected is formatting rules. I have suggested splitting out these rules for quite some time because we use Prettier at Palantir and consider it a better tool for the job of formatting code.

TSLint will continue to release with important bug fixes and updates which keep it up-to-date with the latest compiler / language features.

Update (June 2019): a more concrete roadmap timeline, coordinated with @JoshuaKGoldberg and tslint-contrib-microsoft:

• August 1st, 2019: Stop accepting new core rules. Still accept bug fixes, minor features, and rule enhancements. Custom rules are always an option and can be maintained outside this repo.
• November 1st, 2019: Stop accepting features or rule enhancements (with the exception of ones that make migrating to typescript-eslint easier). Still accept bug fixes.
• January 1st, 2020: Stop accepting anything except security fixes and fixes for crashes introduced by breaking TypeScript changes.
• December 1st, 2020: Stop accepting any PRs 🎉

Update (August 2019): see tslint-to-eslint-config for a CLI command that migrates TSLint configuration files to ESLint configuration files.

Update (March 2020): Added "and fixes for crashes introduced by breaking TypeScript changes" to the January 1st deadline, following discussion in #4914.