A happy thought!!!!
Severus is for all intents and purposes dead...
BUT...
Harry drops the Resurrection Stone in the Forest
Snape's body is never mentioned to be found...
Snape (as Headmaster of Hogwarts) never gets a portrait that we know of...
My Cleopatra (queen of denial) theory is that somebody found that resurrection stone and brought Severus back to life... and he's quaffing Chartreuse in New Orleans and enjoying Mardi Gras!!!
(i won't say he's on a beach sippin' Pina Coladas, cos, well... i know what damage the sun does to pale skin!!!!)