And they are not going to end one way or the other. Here is a recent example. Developer/journalist Tristan Louis did a small experiment the other day:
Louis then went on to examine the code of many top Web 2.0 companies to see how they compared. All of them are using UTF-8, and all of them had errors with the validator. Only five out of the 11 sites have made the transition to HTML5, with the rest using XHTML or HTML v4. As he says, “It looks like there is still much room for improve ment in the world of HTML validation.”
Full article: The State of HTML5 Validation According to Tristan Louis – TNW.
Of course, HTML validation today is not an easy task, when some parts of the code are not even yours as TNW found
In places where we’ve embedded Facebook code on our home page, the Validator considers instructions that include the namespace declarer fb: to be erroneous. What’s more, every part of those instructions generates a single error, so the entire instruction line may be deemed guilty of ten separate counts or more of infraction. The screenshot above shows one example of an attribute (among many in the same line) that the Validator claims doesn’t exist, because the fb: namespace declaration doesn’t exist in the specification. So when Facebook doesn’t comply, we’re guilty by association.
Full article Who’s Validating the Validators? Reassessing HTML ‘Compliance’ – TNW
All in all, there will always be the need from big (private or public) organizations to ensure some level of quality (in the eyes of executives with no understanding of the medium). So HTML validation will continue to be another checkbox in a requirements list. At the same time, browsers will continue to evolve and add new features and major sites like Facebook will continue to do what suits them best (meaning that you will have non-validating code from Facebook on your site). It’s a game you can’t win but one we will continue to play…
This is the blog of 
