Right now, The New Mutants still has an August 28th release date, though it's still somewhat difficult to imagine that happening when not even Tenet is arriving on the big screen until early September. Last week, fans noticed that some international marketing teams had replaced "August 28th" with "Coming Soon," and there's now evidence of further delays.
Two theater chains in Thailand are now advertising a September 3rd release, as are Russia and Denmark. If the date sounds familiar, it's because the exact same one was used in the supposedly "fake" Australian TV spot which promoted a Disney+ debut on that exact same day.
It's an undeniably strange coincidence, but it could be exactly that.
The New Mutants director Josh Boone recently explained that deals are signed beforehand with a movie like this that are meant to ensure a theatrical release, but perhaps Disney can have it play in some international locations and then put it on Disney+ at the same time (that would certainly be a unique move, and one which could test the waters for some of the studio's other releases).
There's an investors call with Disney shareholders tomorrow, so it's possible that plans for The New Mutants could be addressed then. However, most will be more interested in learning what COVID-19 means for bigger blockbusters like Mulan and this November's Black Widow.