Re: Extending BuddyPress with HTML5
IE6 is still used by a majority of people, so in most cases it still needs to be supported. Especially in a business environment.
And just because IE8 is starting to work on becoming a better browser, doesn’t mean its there yet. IE9 is probably gonna be a total waste of time as well.
Using javascript for a theming problem is not a good solution.
Not sure where you read that Google search engine is using HTML5. 
