We can't really pretend that nuclear plants for economically effective any longer. Pretty much all of the oil-fired plants constructed in the 1950s and 60s in California, and about half of the natural-gas-fired ones are no longer economically feasible for operation, and despite the fact that nuclear plants theoretically should be cheaper to operate than the fossil-fuel ones, they haven't been. Cross your fingers and hope for effective fusion, but we're not seeing that so far either.
So it happens that solar and wind crossed the line of being less expensive to sell to California municipalities than fossil-fuel-based power over the past several years. And the perovskite-based cells are looking very promising, and approaching 30% efficiency for tandem perovskite and silicon cells.
Of course desalinization does not have the storage problem that home power does. If you've got more solar power in the daytime, only desalinate in the daytime. And we have lots of desert in which to make that power.
So yes, there is desalinization in the future. I think the real problem, though, is that California has both more people, and more acres farmed, than it can support.