What I want to happen:
Melisandre lays Longclaw on the pyre and begins to chant. Jon's Targaryen blood 'activates' when his corpse is set on fire. He emerges from the flames like a phoenix, a very very pissed off phoenix, and cuts down each mutineer with his flaming sword, fire in his eyese-- he slays Olly last. The new Warrior of Light rallies the North & the Wildlings behind him to battle the White Walkers.
What I don't to happen:
Jon is permadead. The Night's Watch lose The Wall to the Night's King. The Army of the Dead decimates the Boltons and overrun the North. Bran and Daeny play saviour like a shittty fusion of Harry Potter and Eragon.