Seriously, I like microdata, I think it's useful, but this kind of utopian, far-away 'we should use this because it might be better in the future' never got us anywhere. That is the lesson we should learn from XHTML2, not 'adding more attributes is cool'.
Standardized metadata can serve as a platform for other services, not just functionality in a browser. And the common sentiment that "we should use this because it might be better in the future" is a hurdle most standards go through at some point.
On the other hand, you might argue that it's simply a coordination problem (http://en.wikipedia.org/wiki/Coordination_game).
In any case, it's somewhat shortsighted to look for immediate, personal benefits. Of course you need to look at the payoffs for implementing a spec, but I think it's wrong not to take longer-term possibilities into account.
Someday, it would be nice if every single street address on the web was marked up in such a way that just from looking at the markup, a computer can unambiguously figure out the location you're looking for. Or a way for browsers to unambiguously know that something is a phone number and not a zip code (Android does a horrible job of this. Try texting your current location from the maps app.)
I guess, the semantic web remains a dream, but that's no reason to avoid adding semantic data, especially if you want computers to interact with your data directly.
<a href="tel:+44-555-5555">my phone number </a>