Regarding declining sales, I do wonder how much of that is (at this stage) on the dealers/mfr's etc for not taking a harder shot at marketing to the urban crowd.
I took a ride downtown the other day, & was noting that the number of bikes, from 50cc scoots to big cruisers and sport bikes went up the further in I went. Particularly the smaller bikes and scoots (this was about four days before amerivespa, so might have been a couple extra due to that..)
On the west coast particularly & elsewhere from what I can see as well, urban density is going up. The ability to take private transportation you have a prayer of parking has significant value to many. Additionally you get odd stuff like..Bikes are not required to be insured in WA, so insurance is very cheap if you get it. 50cc & down bikes in Denver get a cheap tag, not sure about insurance, but can also park on the sidewalks in Denver. (Was just down there), & similar stuff in other areas.
Those points can make ownership for urban types pretty inexpensive. With a few bucks to make sure that folks are aware of these things, & maybe some to do stuff like increase "moped" definition to including bigger bikes (to allow for 2 stroke vs. 4 stroke power, & encourage cleaner emissions) as well I think some inroads could be made even in colder environments (I rode my old Jawa through most of the winter in MN for moderate distances back inna day.)
Sadly the only real advocacy group I know of is the AMA, & they're all about sport bikes and cruisers far as I can tell from the spam they send me (I am a member).
That being the case, lacking a real push, you start losing folks who might otherwise pick up on the easy, user-friendly, sometime gateway bike..the humble scooter.
Whether you stick with scoots or not after your first scoot, it does at least get the ball rolling.