I was doing Flash/Flex work before I stumbled again into Monkey-X. Given these shortcomings of this old tech, I would still prefer Stage3D compared to WebGL but I see MonkeyX 3D is good enough though for WebGL target.
I still think there will be a majority of Flash communities that will push through or could take over after Adobe's support, particularly Adobe already passed Flex to Apache.org. Not to mention there are still active opensource projects and libraries that depends on Flash for business and making games. There's also LightSpark (Flash for Linux) which is actively being developed (last commit 4 days ago as of today) and Chrome's PepperFlash..
LightSpark
https://github.com/lightspark/lightspark