I think, looking out a long ways, that someday the demand for such a spacecraft will be there. But it's not going to be soon, and frankly, the main reason the Shuttle has so much download capability is thanks to the NRO getting involved. They liked the idea of a launch vehicle where you can't tell how much went up or came down, because it looks the same from the outside in any case. But that cool capability didn't prove to be all that useful in practice. Useful enough to justify using it, but not useful enough to justify the whole expensive program.
So, no heavy download capability in the near future, but I think someday it will be wanted again.