If "sin" is defined as deviation from the way of god, then objectively there is not and never has been any such thing, because there is not and never has been any god. I think that, when the point is reached where the material and ideological conditions exist for humanity to voluntarily and consciously change itself and the world, then there will also be no subjective basis for "sin", because there will no longer be a need or basis for belief in god. At that point and into the future, there will of course still be right and wrong, good and bad --in the sense that of what does and does not conform to objective reality and does and does not contribute to forging freedom from necessity and enhancing the ability of society and the individuals who comprise it to continue developing in an all-around way. Then there will no longer be the notion of "sin."
The notion of "sin," like the common concept of "human nature," is yet another expression of something that is not at all transcendent, unchanging, and unchangeable, but on the contrary is historically and socially conditioned and is viewed differently in different eras and different societies and among different social groupings and classes within the same society.
For example, Aristotle insisted that the concept of happiness did not apply to slaves, any more than to animals, but certainly the slaves of that time --if not the animals-- did not agree with this. In more recent past, owners of slaves and upholders of slavery in the southern U.S., who invoked these arguments by Aristotle as justification, no doubt viewed "the nature" of the slaves, and of themselves, very differently than the slaves did. Today, in most parts of the world, it is no longer considered "natural," or in conformity with most peoples idea of "human nature," to have slavery, but this is because of changes in the productive forces and corresponding changes in the production relations of society, NOT because of changes in "human nature."
To paraphrase Marx, all history is nothing but a continuous change of human nature.
“It is difficult to free fools from the chains they revere.” - Voltaire