This would be nice but how is this going to be payed for? Research budgets are already being squeezed pretty tight given how much the sponsoring organization takes(universities ...), research costs, and congressional attempts to cut funding I just don't see it happening anytime soon. It already costs quite a bit to publish.
edit: Just to give an idea of the costs> http://www.lib.berkeley.edu/scholarlycommunication/oa_fees.h...