There’ll be a CD2 which seems to be a drama CD (source)
There’ll be a reading event in Japan named “Data_12.5_Recitation” on the first February 2015. The confirmed voice actors for it are Aoba, Koujaku, Noiz, Mink, Clear, Ren and Sei’s. Source 1 | Source 2 | More info
Also, a few DMMD voice actors (Aoba, Ren, Clear and Mizuki’s) left messages on their own twitters about the end of DMMD, mostly thanking everybody for watching it until the end. Aoba and Ren’s voice actors reminded that there’s Re:code still coming out and Aoba’s voice actor still added that, despite the anime being over, the DRAMAtical Murder world isn’t ending yet.