It is very probable, especially if nothing is done to stop it. Why is that so hard for you to believe?
Ok, it's math time.
It's hard to believe because it's utter horse biskets. As of today at 4:65 PST there have been 1,195 confirmed cases in California according to the Los Angeles times. Newson made his statement yesterday that in 8 weeks (56 days) 56% of Californians can be infected. That 56% is 22,153,600 people. To go from 1,195 cases to over 22 million in 55 days would require 402,771 new infections EVERY SINGE DAY for 55 straight days.
(22,153,600-1,195) / 55 = 402,771
So did over 400,000 Californians get infected today? Every day that over 400,000 people do not get infected would mean that the there would have to be even more infections in the subsequent days to reach over 22 million in 55 days.