Mature nanotechnology: as demonstrated by the RepRap, it is becoming clear that nanotechnology (coupled with another technology, see below) will sort out quite a few of our problems). Once material wealth can be “made” by a machine that itself only requires energy and raw mass (the most advanced post-nanotech replicators will presumably need only energy) then a significant proportion of the iniquities in life will be resolved and done away with.
Well first I really should point out that every machine ever made only needs "energy and mass" of one sort or another. And as for my earlier comment:
Fusion: in order to supply a crowded planet with sufficient energy whilst maintaining the integrity of the biosphere for future generations (and for ourselves, see below) it is necessary to create an elegant fusion reactor that produces significantly more energy than it consumes. This will remove any further material iniquity. We will have energy “too cheap to meter”, and the means of production will be owned by anyone and everyone. I suspect this will result in a sort of libertarianism.
Yowza. What was my younger self smoking? Bit of a cognitive leap from realisable fusion to communal ownership to libertarianism.
How much have I changed in the intervening years? Sadly not enough. I am prone to making vague statements and leaping from topic to topic without any clear rationale.
Further I still haven't made my mind up on all those ideological questions of capitalism vs. public ownership or free markets vs. command and control. The world is far more complicated than ideologues and ranters on both sides make out and neither side is as fully rational and empirical as they should aspire to be.