I don't see what is fundamentally better about HTML5 over Flash. For starters, HTML5's interactive functionality relies on JavaScript, which let's face it, has a pretty dated object-based programming model based on a really old version of the ECMAScript specification. Flash on the other hand has AS3, a fully OOP language (supports classes, inheritance, polymorphism, true encapsulation) which is a lot closer to Java than anything else. Ultimately JavaScript on most browsers doesn't necessarily execute faster than AS3 in flash (and in the case of Internet Explorer, that's still like 60% of the market, it's
an order of magnitude slower!), it's less flexible, the development tools are vastly inferior (I mean Flash has a wide range of tools for content creation, from Flash, to Flex, to Flixel, with various different types of development in mind). The real issue I see for content developers here is that the different platforms will in the end, end up implementing the specifications for HTML5 slightly differently - do you really think that johnny vector-graphics really wants to debug or recreate his funny Canvas video just because of a strange rendering bug in Internet Explorer 10?
Flash itself isn't a CPU hog. Poorly implemented Flash applications are a CPU hog, at least not any more so compared to other scripting-language dependent multimedia platforms. I think Apple are only playing the HTML5 card to shift the focus away from their incapable last-generation ARM CPUs - they know that HTML5 won't gain adoption very quickly because of the lack of content creation tools, and so they don't have to worry about this generation of devices having to run such content.