True, and that's why I mentioned only Mozilla - I have no clue what others are saying. Any references to position of Opera, Microsoft and Apple?
"""Netscape-style plug-ins are supported in Internet Explorer 5.5 Service Pack 1 (SP1) and earlier, but are not supported in Internet Explorer 5.5 Service Pack 2 (SP2) and Internet Explorer 6.""" -- http://support.microsoft.com/kb/306790
I just remember, that there were two versions of Flash - ActiveX for IE and NPAPI for all the others.
It's possible that Mozilla will come around, if Chrome gives them a big enough kick in the pants. Then again, it's equally possible that PNaCL / PPAPI will remain simply an app distribution mechanism for ChromeOS.