1) Adobe is effectively stopping work on Flash for Linux on their end; it's just not worth it to them.
2) Google is going to support Flash for Linux for Chrome specifically. They can do this because they have access to Flash source and because the Pepper version of the plug-in is much more cross-platform than the NPAPI version, so the support effort is not too great. Given that they already ship a modified Flash, not the stock one, it's not that big a difference from what they're already doing.
So I think you're wrong; even if other browsers implemented the Pepper API, they would also need source licenses from Adobe or would be dependent on Google to get the Flash plug-in.