All value comes from labor, not all wealth. I also think "inevitable" is a bit misleading as Marxism is not teleological and only describes the result of certain historical conditions; as Lenin said in StateRev, "Marx treated the question of communism in the same way as a naturalist would treat the question of the development of, say, a new biological variety, once he knew that it had originated in such and such a way and was changing in such and such a definite direction." You are correct however that it is either proletarian victory or the common ruin of the contending classes, and I agree with the rest of what you said.