Re: "whether the global keymap C-x 4 will be replaced by a command,"

[Juri Linkov]

> What would it mean to replace that keymap with a command?
>
> What would that change for users?
> Would that make help commands give less useful results for C-x 4 C-f and so 
> on?

It's easy to answer your questions by just loading the package
other-frame-window.el from GNU ELPA, enabling other-frame-window-mode,
and seeing how it works.

By default, it uses 'C-x 7' for the other-window prefix
to support such keysequences as 'C-x 7 C-f'.

Trying to type 'C-h k C-x 7 C-f' ends the keysequence after
'C-h k C-x 7' and displays the help for the other-window command.

This means that after binding the current ctl-x-4-map in Emacs core
to the other-window command, 'C-h k C-x 4' will display the help for
that command, not for the whole sequence 'C-h k C-x 4 C-f'.