As I said previously, I expect this issue to become more and more common, and that if customers ask for it frequently enough an inexpensive solution will be provided.
Consider that the PV system inverter is controlled by some sort of microprocessor, and I expect the same is true for an inverter generator (which are becoming more common), and that the issue is a controls problem, not a physical impossibility. To make this work would require the correct and compatible software on the two systems, which would not be trivial, but which would be an engineering expense that doesn't particularly change system production costs.
-Jon