Regardless of the academic merit of the idea, there's some funny business in this economic argument:

"Removing the approximately 100,000 children who would no longer be eligible to start kindergarten would save about $700 million a year, according to the independent Legislative Analysts's Office. Those savings would continue through the 13 years the children would have been in the system, adding up to $9.1 billion, Simitian said."

The savings will only be in one year. The kids born from September 1 to December 1 can't enter in the first year but they will enter in the second year. During the second year, there will be fewer 4-year-olds enrolling but there will be an equivalent increase in the number of 5-year-olds enrolling (due to the kids who deferred for a year).

Agree with Fuzzy Math here.
There is no 'savings'. you are simply shifting expense back a year. All those kids you don't let go to school this year will go next year. They aren't going away. The shift happens over 3 years (not one as in Fuzzy's explanation), but the result is the same.

Additionally, beyond the teacher petition, are there studies that back up the change? Watching my 4 1/2 year old grow up, i personally think we could be teaching kids more, earlier. She learns so quickly and her mind is totally open, especially to language. why do we wait so long to teach language?

I would like to see some real documented statistics here on the rate that "Almost every child who comes to me for reading support has a fall birthday. They don't catch up somehow down the line. Instead, they end up on everyone's radar."
I think that is a pretty bold statement to make with no evidence to back that up.

I agree that the expectations for kindergarten are too high. Having kids younger than 5 has tremendous effects later in elementary or middle school. In many cases these comes because the children were too young. If we continue increasing the academic expectation, we need to prevent that young children wait a little more to be more emotionally ready to sit learn and follow rules.