According to this article
link as of 2010 Georgia has more than 14,000 acres growing blueberries. Based on my travels through the state, several of the counties have acreages dedicated to blueberries. Though I've never been I have heard that Bacon County has had an annual Blueberry Festival for many years so I would assume it is one of the larger growers.
From what I have seen most of the blueberries today are machine harvested. Although humans do run the machines and probably do some, if not all, of the sorting and packing I still find it hard to believe that a decrease in illegal immigrants is going to destroy, or even come close to destroying, the blueberry industry. In my youth, back before machines harvested most crops, high schoolers, and sometimes younger folks, on summer break did a lot of harvesting. I began working in the tobacco field driving a tractor pulling a harvester when I was 8 years old. This harvester had 4 tobacco pickers (humans) and 4 stringers (humans) and usually two humans stacking the full sticks and providing empty sticks. By 9 years old I was picking tobacco. At no time was there ever trouble finding help to do the harvest. At no time were there illegal immigrants involved.