Ewing participated in an interview on the Marvel website last week where he elaborated on what's going on with Iso-8 and what it does. The high points:
* As made clear in Ultimates, this is the same as Neutronium, Blue Marvel's area of study, now in a stable configuration since Secret Wars and therefore both usable and existing in great supply (particularly in 'Battlerealm', the remains of the Secret Wars universe).
* While it's not stated outright, Ewing makes clear that this is the material of the Cosmic Cubes, which were previously made with artificial Iso-8.
* S.H.I.E.L.D. got some Iso-8 in Captain America, though they may not be fully aware of what they have on their hands.
* The 'Iso-Sphere' being constructed by the Collector in Contest of Champions "makes the cosmic cube look like a lump of burnt coal".
* Iso-8 acts as a 'cosmic counter' of iterations of the Marvel Omniverse (rebirths of just 616 or other parallel Earths, as Ewing notes, are a dime a dozen). The previous, 7th iteration of the Multiverse (presumably home to the unstable Iso-7) was what was destroyed in Secret Wars. The 6th was Galactus' universe, "a place of pure Kirby science", while the 5th was a realm of dark magic home to Moridun, who's causing trouble in Ewing's New Avengers. He has rough ideas for the first four universes, but that's something to be explored much later on.
* Cosmic artifacts of major power are going to be proliferating like never before as a consequence of Iso-8's very existence.