That's a good question. Some question whether they flourish now. Southern California does not have the landscapes of apples, pears and peaches of Oregon, Michigan, Pennsylvania or even Fresno, but there are nice little niches of persimmon, low chill apple, and even blueberries that thrive in the lower winter chilling environments along the coast and in the south of California.
Here is an example of what might happen to this fruit industry here. A recent, detailed study extrapolate the accumulation of cold periods in Spain over the next 30 years and to the end of the century. This provides growers with important information on the viability of future fruit cultivation in the various Spanish regions, as it allows them to know if there will be the necessary accumulated cold for the fruits to grow correctly or if they should relocate their crops to other areas.
The results obtained show a general reduction in the accumulation of cold in any future period for all the chilling models and scenarios considered. The reduction is especially significant at the end of the century, under the most pessimistic scenario. These results invite us to strongly commit, not only to adapt but also to mitigate climate change, something that would make an important difference. The probable reduction of cold would threaten the viability of some varieties of fruit trees in the near future, especially in regions where there is currently a low accumulation of cold and there are varieties that require a lot of it.
The study can be viewed at:
https://www.nat-hazards-earth-syst-sci.net/19/1087/2019/
Climate change discussions for California can be found at these websites:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=30513
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=28175
An intriguing Santa Barbara apple study grower's observations are worth noting: https://ucanr.edu/blogs/Topics/index.cfm?start=1&tagname=apples
By the way the 'Moor Park' apricot is not from Moorpark, CA, but from England and the variety has never done very well in Moorpark (http://www.ngr.ucdavis.edu/treedetails.cfm?v=997).
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