Apple iPad doesn't support flash and YouTube has an
HTML5 beta version which is flash-free and supports Safari, Chrome and IE8 with Chrome Frame. Add to that the power of AJAX which can probably replace a lot of the GUI capabilities of flash and it seems like the future of flash is about decline.
It's quite entrenched though so it may take quite a while, but suppose that few years from now all browsers have HTML5 and youtube is completely flash free. Other sites will probably follow suit and these popular video sites are probably the heaviest users of flash. Just this switch alone would probably begin rendering flash to the fringes.
What do you think? And would you welcome this? I think I would. Flash is a proprietary resource hog.