[development] Some of core to contrib?

[Csuthy Balint]

let me try to explain it with an example if I understand your request 
correctly.

module version
core-hybrid: aggregator-7.x-1.x = drupal 7.x
contrib: aggregator-7.x-2.x and above

core-hybrid: aggregator-8.x-1.x = drupal 8.x
contrib: aggregator-8.x-2.x and above

Yes, sounds good, one small step in the right direction, I support this 
idea.. I think it is a similar model how Acquia choose module versions, 
just much more strict..

one thing which I do not understand is what happens with the modules, 
which have files in the "includes" directory, like the menu module with 
menu.inc. I guess it won't be possible to change (improve) the menu.inc 
file in menu-7.x-2.x, but of course there would be a larger pressure on 
core committers if something really have to be changed in those include 
files for the new module versions..