Here's the plan, first we locate the Phoenix, kay? Shouldn't be hard, giant firey boid, makes a great big ruckus whenever it moves.
Then we take Hope, yeah, we put her in a Space Ship. Aim that Ship towards the general vicinity of the Phoenix.
Set the ship off, still aimed at the Phoenix . The two meet in Transit, do the bonding thing, Hope can learn about her newfound powers in Space, ideally a few AUs away from our Sun, then she comes back to earth and from there proceed to restore all of Mutantkind through...how did the Phoenix even DO that anyway? Never mind. But she does whatever it is the Phoenix do to bring Mutantkind back.
Bam. Mutantkind is back and the entire population of the planet didn't need to be sacrificed to do it.
Also, we gotta put Cyclops on Anti-Psychotics.