What would realistically happen if it wasn't legalized?
Also, what has happened to the bill? What sort of timeframe are we generally supposed to expect here for it to become law?
This is not a new law to "legalize" bitcoin. It is a change to the wording of an existing stupid law that has never been enforced which prohibits anything but lawful money, and changes it to include "alternative currency" as not prohibited. This is understood to include things like Bitcoin and other alternative currencies categorically as no longer prohibited.
“…no corporation, flexible purpose corporation, association, or individual shall not issue or put in circulation, as money, anything but the lawful money of the United States.”
And its not even making a new law, just adding comments to the existing one to say that this doesn't prohibit bitcoin. It never did, but could have been read to have done so. There are some Bitcoin companies that don't do business in California partly because of this law, so this may be good news for Bitcoin businesses in California, as it removes a legal risk that otherwise might take a legal opinion letter or other document to form agreements. (Agreements to do illegal things are unenforceable)
This also closes a legal loophole. If I am a Bitcoin business in California and I contract to pay someone bitcoin in exchange for something, and the price of bitcoin goes up between the order and the payment, and if I were a scoundrel, I could invoke the existing law to make the claim that the contract can not require me to do something illegal and so is unenforceable contract... the debt could then be paid with Legal Tender instead.