GAW: Your reason is certainly one of the significant factors in the change, but I believe it is not the only one. Another factor I have heard mentioned is the relative affluence of today’s society makes long-term Kollel possible for a large segment of the population. According to this explanation, this type of learning was ALWAYS ideal and the Gemarra only meant to say that for practical considerations it was not feasible for wide swaths of the community. Even in the current economic situation we are much better off then our ancestors were in most of the Old World. Of course if the problems continue to deepen, chas v’shalom, the Gedolim will need to reevaluate the current realities. Even if the situation returns to the way it was 2 years ago, the Gedolim, I trust, constantly have their finger on the pulse of the Nation to determine what is the proper manner for the community to conduct itself.
I’m afraid I cannot quote a specific source for this understanding of the growth of the Kollel movement.