I think you're starting to get a bit silly.
50,000 years?
Given the caveat that they manage to get these working in the first place:
Do a few numbers on how much pollution the equivalent number (200 fusion plants) of gas, oil, or coal fired power plants would dump in 50,000 years. Or 100 years, for that matter.
I think you'd find that the waste products generated even by an equivalent amount of solar power plants would be nothing to sneeze at.
Some numbers to start with: 1 MWh produces this much CO2:
Coal: 2,249 pounds
Oil: 1,672 pounds
Gas: 1,135 pounds.
Doesn't count the other waste products, or the pollution generated by hydrocarbons by mining, drilling, transport, and other issues.