Will HTML5 Destroy Flash?

Maybe. Too soon to tell. SEO people will prefer HTML5 rather than Flash. Flash is not SEO friendly. In fact, Flash is search engine-invisible. HTML5 will eventually do everything Flash does plus the added search engine optimizations such as Improved page segmentation, A new article tag, A new section tag, A new header tag, A new footer tag, A new nav tag.

In order for HTML5 to overtake Flash, browsers must have to support it, right? Full browser support will happen in 3-8 years? The full HTML5 spec wont be finished (probably) for another decade. Your starting to see improved support for HTML 5 elements in Opera 10.5, and possibly IE 9. Chrome and Safari do support HTML5 video. Firefox is still behind, although I think there are add-ons to Firefox to support HTML video?

HTML5 allow a standards-based pathway to busting those Flash barriers with canvas graphics, drawing video onscreen, Web Forms 2.0, and local storage for private data. So who needs Flash? The only drawback I see now in HTML5 is that it has very basic support for sound. Who will win? Who knows? This may play out in about 1-5 years (depending on who adopts HTML5). Personally, I think they can both coexist, but I would rather use HTML5 for search engine reasons.