Well from my perspective, I don't know because HTML5 is more hard then simple flash. But depends on what your useingvut for. Like videos or slideshows!
I see Flash fading out over the next few years ago as technologies like 3DML, VML, and VRML, have before it. HTML5 can do so much more than just the video tag that Apple products and some browsers use (Opera 10.51+, FireFox 3+ with a plugin). HTML5 ads more elements like canvas (supported by all browsers except IE), Web Forms 2 (supported by Opera), and tons of other formatting enhancements.
Yes, I'm excited for when HTML5 will become the standard and see what things will come from it. I've already seen demos, and it looks amazing. Flash, on the other hand, is a CPU/Battery hog, and you have to keep updating it if a site requires a higher version.
Apple is the only big supporter of HTML5, because they don't like flash and refuse to use it in their products(other than mac and MacBook). They want HTML5 to take over flash, as other users have said.
HTML5 will go beyond Flash while dissapear like VML, VDML,and 3DML. You never heard of those because better things are constantly coming and soon HTML5 will be replaced! It will just process into better things. Soon maybe a HTML6. But YES HTML5 IS replacing Flash.