I was recently re-reading Bell's THE COMING OF POST-INDUSTRIL SOCIETY. In
the first chapter, Bell devotes an extended discussion to the following article:
Harris, Abrams. L. "Pure Capitalism and the Disappearance of the Middle
Class" JOURNAL OF POLITICAL ECONOMY, June 1939, 328-356.
I got my hands on this article and found it to be extremely interesting and
one of the best things that I have read on this question. Abrams argues
that the disappearance of the middle class predicted in the Manifesto was
part of Marx's model of "pure capitalism" (akin to a Weberian ideal type)
and that when Marx discusses the development of capitalism as a real
pheonoma, he sees the disappearance of the "old" middle class and the
creation of a "new" middle class.
BTW, that's the reason Bell picks up on this article becuase Bell argues
that given the rise of the new middle class we can no longer talk about
capitalism but must discuss "industrial society" and also, like Galbraith
and others, talk about a convergence between industrial societies regardless
of their politcal underpinnings.