It is very rare, very rare, for Google to talk about launch dates and/or when new features are coming to existing products, but today I spotted a thread in the AdWords API Forum where a Googler gave some details on an upcoming feature. A couple months back, Google launched a form of behavioral targeting, they call it "remarketing" in Google AdWords.
Remarketing isn't search ads, it is within the content network and is really a form of behavioral targeting - again, not search. That being said, it is still an effective way to drive traffic to your site and there is potential ROI with the campaigns. Who knows, maybe this will be added to targeting features within your search campaigns, and if so - it can be scary for searchers but pretty sweet for advertisers.
In any event, Google currently doesn't have support for remarketing or audience targeting in the AdWords API. An advertiser asked when will the API support these features and surprisingly, a Googler replied.
Eric Koleda from the Google AdWords API Team said to expect it mid Q3 of this year. He said:
Based on our current estimates, re-marketing and audience targeting functionality should be available in the API around mid-Q3. Please note that while we're sharing these rough estimates to help you plan your API development, all dates are subject to change.
Forum discussion at AdWords API Forum.