Will it really fall into the ocean?

According to another book I read, Assembling California, by John McPhee, geologists are quite certain that a rift will open someday, very similar to the rift between Africa and Arabia that forms the Red Sea. It will allow the ocean to enter a deep trough that will run through Death Valley, up toward Mono Lake, and somewhere along one of the many block faults in Nevada.

So, while California won't literally "fall" into the ocean, it will become more of a penisula with ocean on both sides.