They definitely seem to be spreading to roadside zoos/private facilities, even if there is decline in the AZA. I’ve seen more and more places online offer them, and variegated squirrels are showing up in newly opened roadside zoos and private menageries much more often now.
Prevost's have been in the private trade for years - many of the non-AZA holders have had them for over half a decade. There does not seem to be any real uptick in holders.
I'm also doubtful of Variegated - there's 14 reports from 6 facilities on USDA for a rough total of maybe 3-5 squirrels currently. They're there and indeed are a more recent arrival, but common and on the upswing? Doubtful. Both places with the most recent reports only had one.