According to Osho, realized ones don’t speculate about survival; they abide wholly in the present. Their certainty is immediate, like knowing a headache: they directly experience themselves not as the perishable body but as vast inner space. Space cannot die; only the ‘walls’ (the body) fall. Thus eternity is known through direct realization, not belief or promise.
They feel, right now, that they are open inner space—not the body—so they know the real part of them never dies.