Re:Full quote of what Mark Zuckerberg actually said about HTML5
by mikeryan on Wednesday September 12, 2012 @12:29PM
(#4511452)
Pretty much every modern websockets Javascript library you use these days will provide fallback mechanisms to flash or long polling to provide the same features. Take a look at the supported browsers for Socket.io and its a much larger list then the one you've provided.
Or wait.. they don't for most
http://caniuse.com/websockets