There are aqueducts between the CV and coastal areas. The water goes the other direction.

If desalination becomes widespread, I imagine the water not shipped to the coast could remain in the Central Valley. I don’t know one way or another if this would make political or economic sense.

EDIT: Wikipedia has a good overview: https://en.m.wikipedia.org/wiki/Water_in_California

Water rights are so complicated that they’d probably sell the water to the Central Valley before it ships to them. I think it very unlikely that they’d give them up.

There's no way the water would be affordable for agriculture if it had to pay for pumping it uphill/inland. There's a reason the rivers flow in the other direction.