If there was a cc restriction - I'd be upset - but I can see how the benefits outway the disadvantages. I would really like to see the manufacturers step up with some better - lower CC bikes. Honda's 125 cbr has been a massive success. I wish the rest would put out some more 250's. Kawi's 500cc ninja is an awesome trainer. But thats really only two bikes - and very different bikes at that.
In Europe and other markets where they have the restriction, there are a lot of smaller cc bikes, from the same manufacturers that distribute bikes here. If several jurisdictions (big ones. Like two or three large US states) start putting in the cc restrictions, these bikes will start showing up at dealers here. And the 125/250s that are available here will come in larger batches.
But it's a terrible catch-22. If the law-makers don't put in the restriction, there won't be these bikes around. If they put the restriction on, where are new riders gonna get bikes? The re-sale price of under-limit bikes will skyrocket due to high demand, and it will take time for there to be enough new/resale bikes in the market.