Add note about the planned change of the manylinux default

[joerick]

As per discussion in #1772, note about the planned update of the manylinux default.

[Czaki]

Maybe it will be a good practice to promise that all changing manylinux images should be end of January?

[joerick]

Maybe it will be a good practice to promise that all changing manylinux images should be end of January?

I'm afraid I don't follow your logic. What's the relevance of January? The proposal was to change the default at the end of June 2025.

[Czaki]

I'm afraid I don't follow your logic. What's the relevance of January? The proposal was to change the default at the end of June 2025.

I do not know why I read June as January.
In general, when I read in black documentation, that they promise not to introduce changes in style guide except begin of the year. And maybe having information that a change of some default value will happen only at given month may simplify life.

[joerick]

Oh, I see. Yeah, that's a good idea. We're often beholden to external factors too, but let's see if it works to stick to a June cadence on the next one.

[joerick]

@henryiii @mayeut , approval/review here would be good. Test fail is Travis and unrelated.

[henryiii]

Fine by me, but mostly needs @mayeut's approval.

[mayeut]

Oh, I see. Yeah, that's a good idea. We're often beholden to external factors too, but let's see if it works to stick to a June cadence on the next one.

Indeed external factors do exist and not only for cibuildwheel.
In order for the image sizes of manylinux not to grow too much, I'll try to remove EOL ones (when they can be removed) at the time of the new Python 3.x beta.
Given the release schedule of last CPython versions, this generally happens at the beginning of May.