From an economic standpoint it would be much wiser to just release a plugin for safari that plays flash. Otherwise trillions of websites whould have to be converted to html5 (what will not happen)
If Apple really wants to demonstrate what html5 can do, their page needs to run on ALL browsers (IE9 with html5 support, firefox, chrome...)
Showing messages like "you need to download safari" is just plain silly, flash is a standard that works on 90% of the computers on this planet, why should people change?
Adobe could make flash an open source standard and optimize performance for touchscreen devices but thats it, we dont need to re-invent the wheel, just because apple likes us to do so!