Firefox does still offer an Extended Service Release of their browser that does support the NPAPI plugins that our cameras use for their IP interface live preview. You can download that here. This should last until the end of the year (2017), and we should have another solution well before that.
You can also still use Internet explorer to view and control the cmaeras.
The other option I regularly use is the IE plugin for Chrome. You can view the IP interface preview windows in a Chrome tab then.