With NASA shifting to a Mars focus (and the growing popularity of the Red Planet in media and the public consciousness), there's some exciting stuff on the horizon. A move beyond an ageing ISS to cislunar and deep space operations represents a big step forward both in terms of risk and reward.
Any Mars programme will have to operate independent of Earth to some degree given the challenges involved simply in transitioning between the two spheres of influence. Cislunar operations mark a similar independence - though transfers are less time-dependent, stepping out of Earth orbit means that missions are harder and more dangerous to abort, trickier and more expensive to supply, and must be at least in part self-sustaining.
The rewards are big, however - asteroid mining programs could see the processing of rocket fuel in orbit, drastically reducing the cost of space travel through bypassing the tyranny of the rocket equation. Lunar operations are an excellent staging point for operations further from Earth (most of the delta-v requirements for these are from simply getting out of Earth's gravity well). And the lessons we learn from developing the technology for self-sufficiency and in-situ resource utilisation could be the first steps towards a colonisation effort.
The journey to Mars crosses three thresholds, each with increasing challenges as humans move farther from Earth. Earth Reliant exploration is focused on research aboard the International Space Station. In the Proving Ground, NASA will learn to conduct complex operations in a deep space environment that allows crews to return to Earth in a matter of days, primarily operating in cislunar space. Earth Independent activities build on what we learn on the space station and in deep space to enable human missions to the Mars vicinity, possibly to low-Mars orbit or one of the Martian moons, and eventually the Martian surface.