It will not be more than 10 years. This period of time for the "final completion", all browsers support all parts of the specification. This should become a candidate at the end of this year, at the beginning of next year and, we hope, is approved by 2011.
I’m gradually approaching him where I can, right now. How much I use depends on the audience, but since IE’s share has been steadily dropping, what they don’t support is no longer a killer, especially since John Resig "HTML5 shiv" allows you to use semantic tags even in IE6 with js enabled.
More importantly, I'm starting to shift my thinking to HTML5 strings, using classes today to become HTML5 tags tomorrow (div class = "nav"). This way, I’ll be more used to thinking in HTML5 terms when the opportunity arises.
Arlen
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