Originally Posted by Doitsu
Not necessarily, just as the current epub 2.0.1 standard does not support all xhtml elements, the new epub3 standard won't support all HTML 5 elements.
I.e. the IDPF won't have to wait until the HTML 5 standard is finalized; they can cherry-pick the new features that they'd like to be supported by ereaders using the HTML 5 specs as guidelines.
Both Amazon and Apple already followed a similar approach.
And if HTML5 ends up being different in enough respects to what they have chosen, it can come back and bit them on the ass big time.