Just as post-Shuttle development inevitably includes some kind of Heavy Launch Vehicle (HLV), there is no sound reason to halt development of some kind of manned landing vehicle. Chris Bergin outlines more than one way to get back to the lunar surface without the Ares I/V [NASASpaceflight.com].
Immediate mission requirements, such as logistical resupply of the International Space Station (ISS), is catered for in the FY2011 budget proposal via yet-to-launch commercial vehicles, in tandem with overseas assets such as ATV, HTV and Progress, ahead of manned requirements to take over from purchasing Soyuz seats for US crewmembers during the upcoming gap.
However, the future outlined in the budget proposal only makes a passing reference to an eventual goal of a manned mission to Mars, sometime in the 2030s. It also cancels the Constellation approach to returning to the Moon.
While the SD HLV assessment is not a policy document – instead finalizing all the evaluations into the SD HLV, potentially for the benefit of documenting the work for a commercial entity picking up on the design – the findings do provide interesting architecture approaches for both Lunar and BEO missions.
Part 1: Completed SD HLV assessment highlights low-cost post-Shuttle solution
Part 2: SD HLV review outlines ISS Logistics and Transport
Part 3. SD HLV, Commercial and International architecture outlined