On some days, I see 3 or more, some weeks I see none.
I think the "waving" thing will fade as the cars become more commonplace. When I first got my PT Cruiser, it was still a new model and not very common. We all waved to each other. We thought we were cool, adopting a retro-looking car. After a few years, no acknowledgement at all. PT's were everywhere, used by soccer moms, pizza guys, IT support companies, etc.
I bet the same thing will happen to our smarts once they become mainstream.