In short: we are upstream and we have to focus on moving forward and
keep PHP as its best possible level. That does not mean we have to
break things in every single release but we cannot stick to something
because we have to support the last 5 dead major releases for some
random customers, who rely on distributions anyway (they won't update
using upstream code any time soon anyway).
This. Said even better than I was planning to.
The point perhaps is not 'they won't update' but rather simply that they CAN'T update - it breaks too much! As I've said - I've given up on whether you call the next version PHP5.6 or PHP6 anyway, and I have no doubt that the way PHP is being evolved is the main reason that many end users are simply not bothered with upgrading as well nowadays :(
That said, at some point we do actually want a 'better' PHP6 and the tinkering here is not the main areas that need addressing to roadmap a plan for that!