NewSpace 2012: Space Alternative Architectures.
http://www.youtube.com/watch?v=_jMHgfQPBHU#t=31m31s

As discussed in this blog post by Jon Goff, ULA has argued for applying already known lightweighting techniques, such as using aluminum-lithium instead of steel, to Centaur-style upper stages:

Centaur Based Earth Departure Stage.
Nov 16th, 2006 by Jonathan Goff
http://selenianboondocks.com/2006/11/centaur-based-earth-departure-stage/

According to ULA, on a 40 mT version, you can raise the mass-ratio from the current 10 to 1 to the 20 to 1 range. What’s notable is that this will allow a single in-space stage to make the round trip from LEO to the lunar surface and back again, carrying a Dragon-sized capsule.

NASA is investigating using composite tanks for use on a proposed SLS upper stage, but this is for the Earth Departure Stage(EDS) that wouldn’t even be deployed until the 2030 time frame, if funded:

Boeing Develops Game-Changing Composite Propellant Tank.
Posted by Doug Messier on December 13, 2012, at 5:27 am in News.
http://www.parabolicarc.com/2012/12/13/boeing-develops-game-changing-composite-propellant-tank/

But the 5.4 meter wide version expected to be completed by 2014 could already be used on a 40mT-sized Centaur that would result in an even lighter stage than the aluminum-lithium ULA version. This single stage could be used on the Falcon Heavy scheduled for first launch in 2014 and the SLS first version scheduled for first launch in 2017 to produce a lunar landing vehicle.

Bob Clark

Such was planned as part of the precursor robotic program associated with lunar return. The first polar rover mission was postponed to support cost issues with the Ares I development. When the VSE was cancelled, that mission went away completely.

I would enhance what you wrote by adding further that there’s a lot of remote control or telerobitics work which could be done right now on the Moon (e.g., establishing ground truth for orbital observations, finding concentrations of various ores, doing exploratory drilling for ice at the poles, etc.) using existing ETO launchers like Delta IV and Atlas 5. These telerobots could be delivered to the lunar surface with landers which would require no new breakthrough technologies. Landing such telerobots on the Moon would require neither SLS nor propellant depots nor any form of unobtanium.

We can get started on the road to ISRU and sustainability in space using the technologies we already have in hand now.

Constellation had it’s flaws, but at least we had a destination and a clear plan to get there, like in the days of Apollo when every NASA employee had a printed sign, prominently displayed, that simply said: “The Moon”

Humans are obviously not going to live and reproduce in a microgravity environment until we finally deploy rotating structures that can produce artificial gravity. Yet there is no serious artificial gravity program at NASA.

We also need to find out if humans and other animals can permanently adapt and reproduce under the low gravity environments on the surface of the Moon and Mars without any serious deleterious effects. Yet this administration doesn’t even want to place permanent outposts on the Moon and Mars.

Just being content with humans floating around in inherently deleterious microgravity environments, as we have for the last 40 years since the end of Apollo, or funding manned stunts to the asteroids is a huge waste of tax payer dollars.

NASA needs to be allowed to focus its manned spaceflight efforts on pioneering the solar system again so that privateers can use that knowledge to colonize and industrialize the New Frontier.

Its that simple, IMO.

Marcel F. Williams

We have all the technology needed to set up a self-sustaining colony on the Moon. Any missions BELO (Beyond Earth and Lunar Orbit) will require some form of nuclear propulsion. LEO is not the place to assemble, test, and launch such nuclear missions. If the propulsion system is high thrust and high ISP then “fast” missions to mars without a massive radiation shield might be practical. But Mars is not the best destination- all the interesting places to go are moons in the outer solar system. Mars seems to be “just close enough” but all things considered I do not believe so.
As for an asteroid mission that is a waste of time; no possible value in such a human mission.

A Moonbase near the polar ice deposits is the only logical place to go.

As for new technology- what kind of propulsion system is going to be used? Nuclear Thermal Rockets seem the easy (cheap) way to go but really there is no cheap.

Whatever form of nuclear propulsion is used it will be assembled, tested, and launched from a Moonbase.

Anything else is just a waste of time.