While I agree with you that we should move to a post-coal society, I think that the issue of job mobility (from coal to renewable industry) is not as easy as it looks like. It seems that the renewable industry would required a slighly more skilled workforce if we agree that coal miners would potentially become factory workers to build, transport and install renewable energy equipment such as solar panels or wind farms. 
I would imagine that a good deal of miners can be upskilled through targeted training programmes, but this would make sense if the move towards renewables was done by the same company (e.g. Sasol spending money to upskill their own miner workforce in order to redeploy them onto another department).