There’s no date announced yet but we’re busy getting it ready.
It’s best to remember that the spirit of API v1.1 is that you need access tokens to scale your usage of the API. The rate limits for application-only auth’s variant of the Search API are not going to be exceptionally high. Most developers will still want to leverage full user token-based OAuth when using the Search API. Implementing use with a single access token is possible today and, while the ease-of-use will be much simpler with application-only auth, the rate limiting scenario will be pretty similar to a single access token scenario.