There's a new teaser trailer out today, showcasing what seems to be updated shaders, really colorful character designs, and a new logo. Kentaro Miura is listed as something like "supervisory director", and this is the first time he's credited as anything beyond "original creator" in any adaptation. I'm taking Serpico and Farnese's vivid colors as a sign of his involvement. There's also a snippet of Susumu Hirasawa's insert song Hai Yo ("O Ashes") in there.
Shiro Sagisu (Evangelion, the recent Berserk films) will be returning to compose the actual soundtrack.
9mm Parabellum Bullet will be performing the Opening song.
It will air (and be simulcast by Crunchyroll) in July this year, with the principal voice cast of the movies returning.
Anime News Network wrote: Hiroaki Iwanaga as Guts
Kaoru Mizuhara as Puck
Yōko Hikasa as Farnese
Kazuyuki Okitsu as Serpico
Hiro Shimono as Isidro
Hiroki Yasumoto as Azan
Toa Yukinari as Casca
Takahiro Sakurai as Griffith
Akio Ohtsuka as Skull Knight
Unshou Ishizuka as Narrator