I think the most compelling evidence that they wanted to release it online but pushed it back is that they revealed the official website just one or two days after the theatre showings of the trailer. Now the website just sits there without any content, and to me it seems obvious that they wanted to release the trailer as soon as the website was revealed, but ended up delaying the thing for whatever reason. So all I'm saying is that I would be surprised if it was a theatre only experience, because I think the main purpose of the website is to release the trailer there.
An original action espionage film releasing in IMAX on July 17, 2020.
With Inception, I think we got the first poster (Leo standing in ankle-deep water) with the teaser, so I kind of expect the same with this one. Although, with Inception we kind of knew that the film would be about going into people's dreams by that time, and with Tenet we don't know jack shit. I wonder if they'll release an official synopsis with the first teaser.
If it doesn't hit in one hour, then it's definitely coming tomorrow, poster then trailer would be my guess. I'd find no logic to postpone it from online release. Everyone wants to see it, though not everyone has the theater with it being attached to certain movie.