Removing deprecated code in the 5.x generation early in the 6.x milestone will give a chance to early adopters to adapt or raise concerns during their migration.
Comment From: jhoeller
I'm using this issue for early removal of 5.x-deprecated code in 6.0 M1, meaning a first removal pass with possibly a later one following. There are plenty of obvious candidates to remove right away, mostly dating back to deprecations in the 5.1 line. I intend to leave some 5.2.x and 5.3.x deprecations in place for the time being where external code might commonly refer to it still.