It seems that mod_macro makes it into httpd as standard module.
Yes, at least in 2.5/2.6 it will be. I'm not sure it will be backported to 2.4 anytime soon.
Since it already works, I don't see a reason why not.
IIRC seems he wanted to move some things to core and leave the bulk in the module. Making some changes to core just cannot be done on the stable branch, it depends on the change of course.