I don't get IE9. It's not compatible with the legacy IE6 rubbish, and yet not conformant enough with HTML5 etc so it requires much extra work to support compared to FF, Chrome, Safari. Thank goodness for Chrome Frame.
It's not a standard, but I can tell you that tech innovators do not stand around and wait for some committee to decide "Oh yea, uhh lets make HTML5 the standard now". No matter what the standards say, any respectable web browser should be making their best effort to "conform" to the latest technology.