I came to my own theory on this when I saw it mentioned again on one of the boards I frequent and since it didn't ask for our theories (yet) it's killing me now not to at least write it down while it still makes sense.
No Severus is not the one meant to die. That would be far to obvious. Afterall, Severus arrived at the Order meeting with a top secret report for Dumbledore meaning that he had most likely returned from a D.E. meeting.
There is someone else though. Someone who's family had the reputation for having the same beliefs as Voldie, who didn't fear death, and spent a few years in hiding so that they were unable to return to the Death Eaters.
Im not saying that Sirius was evil but if you think about it, it makes sense. I don't recall anywhere mentioned in the books what his position or duties as an Order member were. He very well could have been Dumbledore's spy in Voldie's ranks before Severus ever switched sides (which happens to have been the ssme time Sirius was arrested for the Potter's deaths).
Think about it and let me know if you agree.
If my theory is actually correct (in which I strongly believe it is) then there is no fear in the fandom than Severus will die anytime soon.
Just Remus' two knuts