Hydro is likely going in reverse as many rivers were returned to original condition for environmental reasons. I don't know of any large hydro under way other than expansion of current installations.
Solar and wind, larger foot print for the same power, and to top it off storage for when needed is not simple. I am still not keen on bunkers of lithium batteries so hopefully other solutions for storing the power to when its needed come along.
The only current problem with wind and solar in the US is the lack of it. There will need to be changes as it gets to a higher percentage of the grid but we already have various solutions for that, the main reason for not rolling out the solutions is the lack of problem to solve.
Could you please go into a little bit more detail here? Which pollutants are you referring to? By "technology in place" do you mean "deployed in the field and being used", or something more speculative?
(not disagreeing with you, i am ignorant and curious!)