Add a forward-looking statement for future wheel versions

[jamestwebber]

Continuing to gently push on progress related to the PEP 777 discussion. I opened pypa/pip#13034 and pypa/pip#13035 and to add a message when pip encounters a new wheel version, and there was a suggestion that the message link to a page packaging.python.org.

For now, this page doesn't need to spell out the specifics of a plan, because there is no plan. It could simply say "At the time of writing there is no plan to increase the wheel version. When that happens, this page will updated" and this will serve as a stable landing place for installers to point their users.