In the Nordyke case, after finding that the 2nd amendment did constrain the local government, the Ninth Circuit said, "the Ordinance [prohibiting gun shows on the county fairgrounds] does not meaningfully impede the ability of individuals to defend themselves in their homes with usable firearms, the core of the right as Heller analyzed it."
This issue, too, I think will fall when the "What's the big deal" catches up.
The Heller Court purposely avoided assigning "strict scrutiny" or any other standard on the right to keep and bear arms. The ban on having a handgun in one's home wouldn't pass ANY level of scrutiny, so the Court left any further discussion for a later case.
"Strict scrutiny" would seem to mandate that gun shows be allowed, since it is unthinkable that the county could outlaw, say, a show dedicated to rare bibles.
But Alameda County, which effectively outlawed gun shows by prohibiting guns on "county property", will eventually suffer the effects of "What's the big deal".
The courts will have to find that bearing a handgun while traveling from one's home to one's place of business will be protected behavior. Eventually, Alameda County will witness the comings and goings of many armed citizens despite any necessity to travel into or through some county property. (Much of the road running past my place is county property.)
In the one instance in which the county can continue to prohibit arms, inside county buildings such as those at the fairgrounds, it won't take long for the taxpayers to say "What's the big deal about having gun shows, especially since that is the one time when the county can make some money off the gun owners". A starving government has little in the way of resources to hassle pro-gunners.