They are correct in saying that the end result of socialism is communism, though they imagine that's a bad thing. Communism is the result of socialism working out its various contradictions, just like socialism comes as a result of capitalism's contradictions. Capitalist decay is built into it as a system, but this very same decay is what prepares the ground for socialism.

If you're interested, I made an introductory Marxist-Leninist reading list, feel free to give it a look.