Here's what I've seen so far (I expect the website to update soon too). None of this has been properly confirmed yet by an official source.
- Animedia magazine is reporting that the first episode will air on 5th July 2014 on NTV/BS Nittere and additional stations.
- The timeslot isn't confirmed yet but some people have suggested it will take over the late night slot which is currently used for The World Is Still Beautiful (Soredemo Sekai Ha Utsukushii).
- More characters are being announced in the magazines. Judging by the seiyuu list at the above link, we can probably expect Katakura Kojuurou (Morikawa Toshiyuki), Sarutobi Sasuke (Koyasu Takehito), Takeda Shingen (Genda Tesshou), Toyotomi Hideyoshi (Okiayu Ryoutarou), Takenaka Hanbee (Ishida Akira) and Ootani Yoshitsugu (Tachiki Fumihiko). None of these names should come as a big surprise for the first episode of an anime based on Sengoku Basara 3.
- I'm guessing Honda Tadakatsu will be revealed in the same batch (of course, he doesn't have a seiyuu credit).
- There's a completely unsubstantiated rumour that T.M.Revolution might not be performing the opening theme this time. This could be fake so please don’t panic yet.
Dengeki Online has posted a news report and the website has now updated too.
- The first broadcast has been confirmed for NTV on 5th July 2014 at 25:50 (that's 01:50 on the 6th July 2014 for those of us who don't follow broadcast calendar notation). Less than a month to go!
- The first episode will receive a world premiere at France's Japan Expo at 15:00 on 2nd July 2014.
- The theme song will be Hokkyokusei ~Polaris~ ("North Star ~Polaris~") by Ishikawa Chiaki. She also provided music for the previous anime, the stage play and (of course) for Sengoku Basara 3.
- Colour artwork of Kojuurou, Sasuke and Shingen is available on the official character page. All of the characters voiced by the listed seiyuu are now confirmed (Hideyoshi, Hanbee and Yoshitsugu).
- Kenshin is mentioned as Shingen's rival in his introduction, so perhaps we can expect the God of War to make an appearance during the series later on.
I had to post another quick update as it's now been clarified that Ishikawa Chiaki's theme song will be used as the ending for Sengoku Basara: Judge End.
An advertisement for her next album, Watashi No Kokoro Ha Sou Ittenai, has been found and posted on Twitter. The album will be released on 8th October 2014 priced at ¥2,160 with catalogue number DDCZ-1967 and is to contain five tracks "including Hokkyokusei ~Polaris~, the ending theme to the new NTV anime series Sengoku Basara Judge End".
The speculation on whether there will be a song for the opening too can now begin...