As much as the idea of every passenger being able to eject in the case of an emergency amuses me, I don't think that's going to happen. Ejection seats are expensive, can themselves be dangerous (they are basically a rocket-propelled chair), and pilots in aircraft that use them need to be specially trained for their use. That's not even mentioning how you'd be able to sever the whole top off the fuselage quickly enough, and if you could, what if that system malfunctions in normal operation...!