We're not optimistic about the chances of the aforementioned bill passing in Massachusetts -- or anywhere else for that matter. The government doesn't have a great track record on banning technology -- even when that technology can be put to questionable uses (think radar detectors). And in fairness, no one should expect that her/his license plate is completely private, since by law it has to be on public display.
From where we sit, the best we can hope for is probably some kind of regulation of the data-collection industry. LPRs will likely continue to flourish, but hopefully, states will set new standards to establish how long that data can remain on hard drives before being erased. That would provide a degree of consistency among cities, companies, and private contractors.
Bottom line: LPRs are almost certainly here to stay, and down the road, they'll be supplemented by other tracking devices embedded on our vehicles. You should probably get used to it or consider selling your car.