Mundfish finally revealed when we can expect Atomic Heart to release and even then, the reveal was pretty vague.
Atomic Heart received a new trailer recently, revealing the release date to be in the later half of 2022. There is no precise date and the teaser noted that the release month is "XXXXXXXber". The last three letters narrow it down to September, October or November but the number of hidden letters narrows it down further, ever so slightly.
There are seven hidden letters, meaning the full word would have a total of 10 letters, meaning none of the aforementioned months fit the bill. The reasonable assumption here is that one or two hidden characters refer to the day of release.
With just four letters before the "ber" in October, it either means the month is out of contention or the date format is "DD(space)October".
In the case of November, it would have to be "DDNovember", which wouldn't make much sense due to the lack of anything to separate the numbers from letters. The only viable option for this month would be "D(space)November" but chances are the actual release date will have two numbers in it.
This theory would also mean September is ineligible due to the release date having to be in the "DSeptember" format.
Overall, it looks like October seems to be the currently planned release month but it all just remains a theory for now, until Mundfish officially released the actual date.