Given this statement and the chart that shows solar and wind already being the cheapest energy sources this must mean we can just switch to solar and wind ... right?
Except we know we can't. We know that the variablity of solar and wind makes those impossible replacements for coal and gas. I guess price isn't the only metric that matters.
This is why the most important number is $/MWh for "solar/wind + storage". Storage has to be included in the equation. At current prices that puts "solar/wind + storage" about equal with natural gas, but those prices are dropping rapidly.
Installation times are also very significant factors in reaching emission reduction targets. Waiting 10+ years for nuclear to come online just isn't viable. Solar+storage can be operational at the same scale as a nuclear plant within 2-3 years.
$/MWh is the only real metric that matters.
Edit: http://solarcellcentral.com/images/avg_cost_of_energy.jpg