I don't think any mainstream court will agree with the absolutist argument that the 2A allows citizens to carry arms on all government land, including such places as courthouses, jails, and military bases. However, I think there's certainly room to argue whether they should be allowed in public gathering places.
I am not so much of an absolutist as my post could lead you to believe. But beaches are public gathering places. So are parades, fireworks displays, parks, bus stops, and movie theaters and restaurants.
Any place where people gather could be designated a sensitive place until there is a legal definition of sensitive.
Having won incorporation, we could see the right abrogated, simply by designating any public place to be sensitive.