I'm not religious at all. Hell. I wouldn't even say I have the slightest inkling of a spiritual side either.
Consciousness, in all it's sentient glory, however defies scientific experimentation. It exists and yet because it is the only tool by which we can experience existence one can't experiment on it and actually break it down.
It can't be proven to me that anybody else is conscious. Nor can it be proven to anybody else that I am. And we can identify the chemical and physical processes that cause consciousness, and we can explain why, but we can't explain what it is, because there is nothing by which it can be compared.
And the conditions by which I (me personally) am currently experiencing consciousness will eventually cease to be. But there is nothing stopping those conditions from ever existing again, other than random chance.
So the question becomes if I die, and the conditions by which I am conscious cease to be, but then occur once again at some future point in time, will I be conscious again? Obviously I wouldn't have any memories of this life though, since we are reasonably certain they exist as a part of the physical brain.
Or if you want to get really oogie boogie about it; If string theory is correct, and within the folds of the n-dimensional space an infinite number of me's exists, would my consciousness perhaps just continuously and seamlessly move between "me"'s that are capable of consciousness.
So I think 3 possibilities exist.
1. The cold darkness of non-existence awaits.
2. Non cognizant reincarnation.
3. Each individual in their own experience is actually immortal (but not necessarily to each other).
1 and 3 would both suck for their own reasons, and 2 doesn't really matter because your previous experiences are lost and you effectively become an entirely different person.
EDIT: And I guess for all intents and purposes, none of those 3 possibilities are technically an "afterlife".