At the "Bushiroad Card Game Live 2011" event held on February 27th, a special program of Tantei Opera Milky Holmes
was announced to be aired this summer. It'll be a 25min long program produced by the staff of the TV series. It's unknown whether the program is a recap of the TV series or a new episode.
According to the official blog, the voice actresses of the four main characters will throw the ceremonial first pitch in a game of Nippon Professional Baseball on April 10th.
Source: Bushiroad's blog
Tantei Opera Milky Holmes Special