I think there's a chance that CD box sets may be dead by 2025 so that may spur them to release it sooner rather than later but yeah, the documentary is what guarantees its release in my mind.
I wasn't very clear. I think Get Back will be released on its own and as part of the box set but I think Let It Be will be exclusive to the box set.
Disney has the distribution rights to the documentary.
My guess is that Get Back will be available on its own and Let It Be will only be part of the Let It Be anniversary box set (with CD, outtake CDs and Let It Be & Get Back Blu-rays) that presumably will be out next fall.
Just a guess on my part but I think both of the documentaries will be in the usual Beatles box set (with the album on Blu-ray + CD and the demos and alt takes on CD) and at least the Peter Jackson documentary will be available on its own.
Like I said, the sooner the better but I don't think they care about hitting the literal 50th anniversary date more than they care about cashing in on holiday sales. Not to mention that they'd be releasing a second $100+ Beatles box set in less than 8 months.
Peter Jackson is making a new documentary using the footage shot and audio recorded during Let It Be. I'm just guessing but I think that's going to get released in the inevitable 50th anniversary box set (and Let It Be will remain on the shelf)...