HTML5 doesn't give any special weight to SEO but its is useful for following reason. There is a lot of things that is no more need to define for HTML5. It gives animated looks to your page so you don't need to USE JavaSCRIPT in your page which increase your chance to be crawled very fast. It give a cool and neat looks to you web page as VISITORS will be more interested in browsing your website. Its very easy to validate as a lot of RULES been shorten in this New Version. There are also some other way HTML5 can be help full for SEO.
Microdata will definitely help with things such as classification of aspects of your site. Other than that (like putting your address in microdata and ranking higher locally, putting your author information in there so your little avatar shows up in the SERPs, etc) it won't really weigh heavy in the scheme of things.
HTML 5 is a language for structuring and presenting content for www. this is the advance version of HTML.
Yeah its too bad that a lot of newbies seem to think its a different 'language' when its just the latest version of HTML. but early confusion is normal, I'm probably confused about a fair amount of things without knowing it.
HTML5 is nice and everything, but until Internet Explorer supports HTML5 then you won't be able to roll this out into production. The rate that Microsoft is going, it may be available sometime in 2015. 61seoservices.com
I will inform my developers to stop what they have been doing for the past year immediately. Internet Explorer users always lag behind in being able to see or use the features available in every other browser. But they don't miss it because we work around their failings. Even in 2015, though, they will only get the capabilities available in every other browser today. Only people who don't know how computers work use IE.