As long as there is fragmentation then flash will not be obsolete. For example the lack of a common supported audio format or shader language in browsers to name two.
With ASM.JS and Native Client Unity can basically run their plugin without needing a plugin :) For the rest of the browsers there is still ASM.JS (which just runs slower on browsers not directly supporting it) or the native Unity Plugin. So for Unity Technologies, Flash is pretty much obsolete.
