"I am not sure what you mean. I used to live in California, they had their own income state tax forms and tables. Unless you mean the tables are based on the Federal tables?"
What I meant was that every state tax form that I have ever seen (and I must confess that I am not familiar with Kaly-fornia's) uses either AGI or taxable income from the individual's 1040 as the starting point in computing state taxable income. State income tax returns are typically relatively simple, at least compared to federal returns, because all the preparer has to worry about are a few adjustments between state and federal law.
If Americans are no longer completing 1040s, then each state would have to develop its own system of computing taxable income from the ground up. IOW, its own IRC would grow greatly in complexity.
That just isn't going to happen, at least not across the board. Furthermore, those states who attempted such foolishness would see their economies stagnate relative to their more prosperous and progressive neighbors.
State income taxes will go the way of the dinosaurs shortly after the FairTax is passed.
I know here in PA they have already stated that should this happen they would probably follow suit.