Going into production later in the year apparently, given that you'd assume the script is developed or pretty much finalised. I never bothered with s3 after it became the bo katan show but I gather s3 wrapped up loose ends of the tv show so it wouldn't surprise me if this is instead of season 4.It’s “announced” just means somebody somewhere is maybe thinking of possibly developing a script for it.
It’s likely something else that’ll never see the light of day. Though I’ve seen people suggest that this might just be S4 of Mando and condensed into a film so they can release it at the cinema and actually make money from it (lol).
Streaming looks to a busted flush for revenue so we might actually see more of this sort of stuff.