It seems they plan to release it on February 7th (though this can obviously change). Once it's released, historically the hard fork takes place about a week later. You can keep tabs on its progress here:

Hardfork 17 - Protocol Cleanup and Simplification
Due by February 7, 2017 48% complete
The purpose of this milestone is to: Fix outstanding bugs (Equihash) Remove as much as possible from consensus bandwidth rate limiting comment posting depth 4 post rate limiting Enforce transaction constraints that will exist once multi-chain fabric is deployed separate voting from content in same transaction

https://github.com/steemit/steem/milestone/13