In regards of GT, except some long time heavy spenders having all(or pretty much all) heroes at least o2,noone in my guild has any big savings of any coins. All needed to gear up as many heroes as possible.
A lot, including me, also skipped farming from Elite, except the real must haves like IE. All stamina goes to gear farming chap17/18
So 6* would be a big time hit in face.
Level cap increase (and new gear tiers) is different thing...