Okay so issue 705 is supposed to be it, Jane is said to perish in that issue, and we are all hoping the hammer goes back to the real THOR and he is restored.
We've seen images of what appear to be THOR with a golden prosthetic arm and golden hammer. Supposedly a new hammer but.....
What if in the final fight with Mangog the cosmic storm is freed from Mjolnir and merges with jane? She is no longer THOR but becomes one with the storm or some such garbage, and the hammer now being cleansed of the storm turns golden in color and it returns to THOR and we learn that THOR's doubts caused the storm to take control of the hammer thus he and ODIN couldn't wield it.
After all, Stormbreaker is made of the same uru as Mjolnir yet is golden in appearance....
I think Thor's new golden hammer and arm is from Adamantine. This metal is from the Greek Gods and is the material made out of Hercules mace.
Remember in issue 702 or 703(if I remember correctly), Jane asked for Hercules help in the War of Realms. After Mangog rekts Thor and Odin, I think Odinson's arm shattered. Hercules would probably take him to Olympus and get him an Adamantine arm and hammer.