On the Shuttle program, I see the end of NASA's program as the transition point in the space business where government subsidies end and the private sector takes over and runs with it. Kinda like when the the Internet was opened up for commercial use in the early 90s.

Of course, this doesn't take in account the plans of other countries (mainly rising powers) for manned flight and programs to travel to the moon and mars. In fact, how their role plays out in space exploration might be a function and an indication of their status as players in forming the human experience in the years to come.