No date announced yet for the premiere. The new PV is here. Check out the ANN article for additional information. Synopsis of the first season from AniList:
In the land of Terra, natural disasters of unknown causes have been occurring irregularly in many areas. Therefore, the majority of the people, in order to escape those natural disasters, came to live in mobile cities developed over the years. The Originium left behind at the site of such Catastrophes, has led to the rapid progress of civilization due to their immense energy. But it also brought something else with it — an incurable disease called Oripathy.
Because the bodies of those with Oripathy gradually crystalize and become a new source of infection at the time of death, in many countries, the Infected are subject to persecution under regimes of segregation and forced labor. Those who were oppressed by the governments are starting to rebel. Rhodes Island, a pharmaceutical company researching a cure for Oripathy, takes up their arms and starts a conquest trying to save all the people from the disease.
Source for the teaser image is the official twitter.
Damn, a 3rd season? Not everyday you see a gacha get 3 seasons of anime. Is it good?
I have heard generally good things about Arknights, but haven't watched it myself. That stands in stark contrast to what I hear about most other gacha-inspired anime though (like Blue Archive this season).
It's good enough that I'm actually looking forward to this, and was very much hoping there would be more seasons. It's not anything groundbreaking but it tells the arknights story well, and that story is a pretty good one.
As someone who have years in arknights gacha can say it is good. The biggest joke is that Hypergryph company behind Arknights creation is a music company and then Gacha and etc. So music direction is always great in all PV for events or character songs. I would say they first season bit lore heavy and is worst in terms of story, mostly rough start of gacha story that was revised. Second season and Third is where the peak of AK storytelling... There is a lot to cover storywise so 3rd season won't end Chapter one (out of 2 which ending soon on CN, global is behind as typical gacha but by 6 months only).
So moving away my bias as gamer and purely on anime. I would say it's decent and good if you can close your eyes on some aspects. The minus are typical anime tropes of child protagonist, amnesiac main character, child is face of the organization. Pluses would be that it is really grounded world building with big premise on suffering of incurable disease and treatment of poor/ill/different race and even specific racism against one race.
So give it a thought, if you enjoyed a bit first season then second will be even better.