Warning: SPOILERS for Immortal X-Men #10
The X-Men's biggest resurrection law has been broken, and with it goes any possibility that the Krakoa era will end. The phenomenon of mutant resurrection, in place for over four years in real time, is now the status quo in the Marvel Universe; the X-Men can now return from the dead with relative ease, thanks to the power of five unique mutants with extraordinary abilities. But Immortal X-Men #10 reveals that the X-Men no longer need all five to bring a mutant back from the dead.
The secret of mutant resurrection lies with the unique properties of Krakoa working in conjunction with Professor Xavier's Cerebro and five mutants, known together as The Five. Egg creates large golden eggs to be used as incubation chambers, Proteus makes the eggs viable, Elixer induces cellular replication, Tempus makes the mutant inside grow at an exponential rate, and Hope Summers enhances everyone's abilities. Mr. Sinister's large genealogy records also allow for this process to happen - but without Hope, mutant resurrection simply will not work.
That is, until the events of Immortal X-Men #10, written by Keiron Gillen with art by Lucas Werneck, in which the X-Men are left reeling after Mr. Sinister kills Hope in a horrifying surprise attack. Synch manages to replicate her powers long enough to resurrect Hope from the dead, allowing mutant resurrection to resume. After the X-Men fight and eventually capture Mr. Sinister, it appears resurrection is safe, but only by breaking mutant rules. However, this is not the first time.
Hope Resurrects, And The X-Men's Biggest Reboot Rule Is Broken
In the penultimate issue of A.X.E: Judgment Day, also written by Gillen, the X-Men decide to resurrect Captain America from the dead using mutant resurrection - despite the fact that the process was never meant to work on humans. But according to Nightcrawler in that issue, it was not a law, but "tradition". Perhaps it is that same tradition that is broken here, and only Hope's powers are integral to resurrection rather than Hope herself. Since other mutants exist that can copy and replicate powers, this means Mr. Sinister's efforts to destroy the resurrection process are in vain.
With resurrection preserved even in the event of Hope's death, the only true way to prevent mutant resurrection is to defeat all five mutants, Professor Xavier and destroy Mr. Sinister's records all in one single attack. Since this is incredibly unlikely, it appears the Krakoa reboot will never be erased, and Krakoa is the new status quo. For the X-Men's enemies, this is a terrifying prospect - even with the death of Hope Summers, mutants can't seem to die.