I have not seen any evidence that solar+wind will provide a proper base load of electricity, and it looks like MSR and its variants will give people the electricity they need.
While nuclear plants do pair well with storage (many pumped hydro storage stations were built to pair with nuclear plants), the idea that they cannot load follow is a myth. It is simply more economical for them to run at full load since fuel cost is a very small portion of nuclear operating expenses.
Every non fossil source except hydro requires a large build out of grid scale storage.