As we reported a couple of days ago, Blizzard updated their Runestone page and this evening there is a Blue post on the subject. Interestingly (and disappointingly), it states that Runestones still need a lot of design work and they appear to be really fine-tuning this system and probably will do for as long as they can.
Now it appears ranks 5, 6 and 7 would be Inferno-only and not in some post-inferno state as was speculated.
Ranks 5, 6 and 7 could still drop, but they would be Inferno-only, and there’s still a potential for some ranks to be crafted-only.
Jay may be able to speak a bit more about Runestones at BlizzCon, but we’re not expecting to have any details finalized this week.
Looks like we’ll have to wait until later than this week until we find out more but this is another important area of the game the dev team appear to be reworking.