Yet more possible (or current) breakthroughes in technology together with a very basic description, critique, likelihood and timescale.
Development: Artificial intelligence
Likelihood: Medium to High
Importance: Supporting pensioners, teaching children and re-educating adults amount to as much as 50% of our economic output. The equivalent costs for AIs would be insignificant. AIs would be able to colonize the solar system more effectively than people. AI labor could move around the globe almost instantaneously lubricating the cogs of the global economy.
Drawbacks include: Changes in the balance of power, massive unemployment, biological warfare becomes more likely, cloning of AIs contributes to loss in individuality and a new type of political system becomes necessary to deal with unequal minds.
Time Scale: 20-60 years.
Development: Materials with high tensile strength >60GPa
Likelihood: Very low to Low
Importance: The stronger a material you have the lighter you can make various forms of transport. Aircraft, cars, ships and space ships would all become more efficient. Space elevators and sky hooks would become possible opening up cheap access to space.
Drawbacks: New types of weapon.
Time Scale: 30+ years.