To tie previous references to fusion power and the cost/benefit aspect of going back to the moon together - Helium 3. There's apparently enough of it in the lunar regolith (cooked up by solar radiation in some way perhaps others here can flesh out) to make everyone's balance sheets, whether they be written up in chinese, russian or english, stay in the black. (Geez, a NuSpaceRace to go with NuTrek - Welcome Back 1960's!)
Fueling the comparatively user friendly deuterium-helium 3 fusion reaction is apparently worth the trip on its own.
Technical limits will be overcome, as always, after fiscal ones are.
How close is this to reality? We need an economic reason for space travel, until there is one space exploration will languish just like it has the past 30 years.
http://www.asi.org/adb/02/09/he3-intro.html
This link offers up some of the numbers making mining lunar He3 worthwhile.
Commercially viable plants using any fusion cycle haven't left CAD screens yet. We won't be going back to the moon tomorrow, but when we do, you can bet that the "He3 Rush" will be front and center.
I suggest googling terms like "lunar Helium 3" to see what other related info might be out there.