re: Addend...
The HST was expecting 2 more visits, I believe.
It will have to be the Shuttle (new devices to replace old ones, etc...)
The ATV is the right kind of vehicle to replace both the Progress and the Shuttle, once the ISS is built.
While there are short duration flights possible, for a capsule, it might be wiser to only use them for long duration flights and do the same kind of missions the Russians did with Mir:
One or two or more astronauts might return back to Earth with an older capsule, that has docked to the station for 6 months (or a whole year). The other astronauts would spend months in the ISS, with their capsule right there.
Raoul