Seo_Mike - 7:53 pm on May 11, 2011 (gmt 0)
I think that regardless HTML5 is necessary to learn for any developer as it will be the standard at some point. More and more big companies are putting investments into HTML5 and CSS3 as long as that continues I can't see this going away anytime soon.
The problem I have is not knowing how to gage the current state of where browsers are accepting html5 as a standard, until this happens it will be a game of trial and error.
On a personal note I use html5 for my code and am enjoying the ease of the <canvas> feature and much more.