Despite the fact that we were talking about the industry association making this move, and not individual firms, your question cuts right to the heart of the matter, and my answer is a qualified "yes".
I should clarify that I have no inside information to share despite my company's relationship with Avigilon, so these are just my thoughts...not facts or even speculation based on facts from within that company.
They will enforce the patents. They have to. But I think the likelihood that a manufacturer will run afoul of them just went way down. People in the industry know the history of the OV patents, and how they have yielded dividends...and they think they know that Avigilon will ruthlessly enforce the patents, thus reducing the need for actual enforcement.
Back to the original question of whether SIA will get involved: absolutely not. That'd require too much coordination between major manufacturers with their own patent portfolios and legal considerations to think of.
TL;DR: Yes, Avigilon will enforce their patents, but will not have to worry about SIA stepping in, and manufacturers are more likely to avoid these suits now than ever before, IMHO.