There is another thread I saw that asks the same question but for a broader topic: This should have an Anime!. I'll let this one go.
Immortal Regis....followed up by Cavalier of the Abyss.
Did you know Soul Eater Not? might start a new anime?
Chiaki Omigawa, Maka in Soul Eater, confirmed on a live Nicovideo radio program the teased news that that spin-off Soul Eater Not! is getting an anime adaptation.
The Atsushi Ōkubo manga follows three girls in NOT (Normally Overcome Target) track at the Death Weapon Meister Academy, as opposed to the battle-oriented EAT (Especially Advanced Talent) students of the main series.
The man who did Kongou Bancho also did Seven Deadly Sins. SDS's anime is in the works. I'm not sure about Kongou Bancho. For older manga series that already ended, there is not much of a chance to get an anime adaptation. I never seen anime adaptation of manga series where it's done.
I can't think of any other manga series. I should have edited off Buster Keel and Yotsuba. They won't animate those manga series ever.