Flash is under fire from all corners at the moment:
- The release of HTML5 and subsequent testing by Google of a Flash free YouTube. HTML5 will play video without the need for any extra plugins such as Flash.
- Apple won't be supporting Flash in the iPad or on the iPhone. So that's a mobile barrier.
- SilverLight is a competitor and has the weight of Microsoft behind it.
I think that Flash is established on enough people's browsers and is standard enough that even if they were to stop work on future versions of Flash today it would still be around for a few years to come. I mean people are still using IE6! As it is Adobe are on the ball and I have no doubt will keep Flash relevant in the future for web developers.