I feel I should point out that ARIA definition and support is progressing very quickly (compared to just about any other W3C spec), but I’m fairly sure you know that already. E.g. IE8 has some support for ARIA, but none for HTML5.

I’ve seen no evidence that WAI-ARIA has distracted or detracted from other specs. What has been very difficult is getting accessibility requirements taken seriously by some people.

A key quote from later in that thread is:

we can’t just afford to punt on the concept of a directly accessible <canvas> … In HTML 4.01 the W3C made similar errors with JavaScript and CSS and said you had to be accessible with either technology turned off. Developers were saddled with these handcuffs for over a decade.

I don’t see things in HTML5 that could have made web applications accessible today. That’s not a criticism, these things take time. However, you have to try and minimise the gap between new technologies (e.g. AJAX applications like Gmail) and being able to make them accessible. WAI-ARIA fulfils that.

ARIA can make HTML5 simpler because it covers things that HTML5 doesn’t. It also appears that Hixie is waiting for ARIA:

Yes, the plan is to make sure ARIA and HTML5 work well together. Right now I’m waiting for ARIA to be complete … Once that is cleared up, I expect HTML 5 will give a list of conformance criteria saying where ARIA attributes can be used and saying how they should be implemented in browsers.

I think that’s fair enough, as there’s probably more than enough other considerations for the editors to deal with, and the people working on ARIA will have better experience with accessibility issues.

So the question for you is: What things haven’t happened that would make ARIA redundant?

By the way, I couldn’t see anything directly relevant from your link, perhaps ARIA in HTML5 integration is more relevant.

The real solutions could already have become the ones that work today. If only had ARIA not been distracting (and frequently detracting!) from them.

ARIA is not a solution for the here-and-now. It is a cause of there still being a problem in the here-and-now.

Incidentally, HTML5+ARIA integration was underway in late 2008. How can ARIA be making the HTML5 specification simpler when this has taken over 2 years, so far?