Although there has been progress to use coal plants as variable output plants, they tend to be used base load plants that run all or most of the time. The same thing is true for Nuclear plants, and to the extent that power prices occasionally go _negative_. (This essentially means that the utility is willing to pay people to take their power for a brief time at low system loading, so that they can avoid turning a plant down or off.)
Renewables are used differently, in that there's a lot less ability to rely on them to generate power. So they're not really a replacement. This makes me think the ability to shutter these coal plants is a lot more dependent on the decision to extend the life of the nuclear plant and buy the NG plant than it is to do with the renewables they're adding.