Now the thing we only know is that there have 8 OVA of Black Butler, and they would not released on TV. From the story, we could find that the season is one foreshadowing, how the story progress would become the biggest suspense of the 2nd season Black Butler. At the beginning, there have some news said that the 3rd season would be shown on July, and then it was confirmed they are disloyal.
Usually, popularity and expectation value decide the release of one animation, as Black Butler, now the 2nd season is finished, and the ending did not give people a clear result indeed. To some extent the 3rd season may be published, however, it is not now; the interval time should not be so short.
In other way, the anime of Black Butler is not have not support so many content to adapt into OVA. At the 1st season, there are some content have catch up with the plan of anime, so the season is only have 12 chapter. Of course, we know, the 3rd season is everyone’s expectation, so let wait the official news patiently.