SAI157 said

Mozilla announced last year that it will stop support some legacy technology and as we know Firefox will block flash starting August 2016.

Most Flash will NOT be blocked in Firefox 48. There will be a specific list of SWF files that are blocked, based on their apparent use in tracking (browser fingerprinting or settings Flash "supercookies"). So far, this list is pretty short and it's unlikely to affect typical web use.

It's conceivable that at some point, Firefox will no longer automatically activate Flash by default on sites, but require site-by-site activation, as is common for most other plugins. Users may need guidance in how to use that feature if they haven't encountered that before.

Regarding the longer term issue of NO Flash plugin:

Some Flash-based sites might never be updated. There either will be another technology to view those sites or there won't. Mozilla had a project called Shumway to convert Flash to HTML5 on the fly, but that is no longer expected to be built into Firefox. Others could use its code for an extension or... who knows??

I don't know whether it's relevant to your legacy sites, but you may be familiar with Oracle's approach to this problem: Java Web Start.

https://www.java.com/en/download/faq/java_webstart.xml

Adobe has a stand-alone version of the Flash player for developers, it might be called the Projector. I don't know if there is a way to send Flash content from a web page to the stand-alone player and have it end up with the same connectivity supplied by a browser. You could try Adobe's forums to follow up on that or other possibilities.