They might announce it in January.
Check out this article from the LAST logo change in 97:
The Dolphins have announced that they will hold a press conference to unveil the new logo and uniforms on Tuesday, January 14th, at 12:00 noon. The Dolphins Endzone is planning on carrying the event live on their web site, using live audio to allow fans to listen in on the conference.
In related news, Dolphins' President Eddie Jones has said that the team will be taking comments from the fans about the new uniforms and logo throughout the spring. If there are enough negative comments, the Dolphins have left open the possibility that they will not adopt them.