Per a study discussed in this article, it is cheaper to build solar panels or cluster wind turbines than to keep operating coal plants.
On average, solar is a third cheaper than coal.
Coal is not going away in the short term. But, if it is more cost-effective to operate wind and solar, it will be harder for investors to justify investing money for upgrades to coal plants versus putting that same money against alternative energy options.
This is not news, as we have seen this for a number of years. But, any new study that confirms prior studies, add validity to the trend data.