It seems safe to assume that by “this year,” Manganiello meant The Batman starts filming in 2017 – as in, within the year ahead. Affleck is going be spending much of this month promoting his latest directorial effort, the Dennis Lehane gangster novel adaptation Live By Night (which Affleck also stars in), ahead of its Oscar-qualifying limited theatrical debut on December 25th. Manganiello could mean that he will be doing costume fittings or script rehearsals this month (as Batman-News noted), but there’s been no indication that Affleck is prepared to start rolling camera on the film within the next three weeks or so.
Between The Flash not having a release date at the moment – with its previous March 2018 date now being reserved by Warner Bros. Pictures for Tomb Raider instead – and Aquaman shifting back to Fall 2018, it appears as though WB has cleared out space for The Batman to hit theaters in the summer of 2018; based on the assumption that it will begin filming by spring of next year, like Manganiello previously said. Ocean’s Eight is the only summer 2018 tentpole release currently on WB’s docket, so a Batman movie would fill that opening nicely.
Where, exactly, The Batman will be released in that season is the question, given that Aquaman‘s old July release date is now being occupied by Mission: Impossible 6. Seeing as the summer 2018 release slate is pretty packed full as it is (with the competition including two Marvel Studios films, as well as Jurassic World and Transformers sequels), expect WB to make an announcement about The Batman‘s release date within the first quarter of 2017 – before Affleck starts principal photography.