I don't think it's as much Twitter killing Google, as it is a recognition that there's something new bubbling up, where Twitter is the poster child. While Google has dominated traditional search, this might be an area where one can grab a foothold. That's as much as I read into it.
I have routinely found recent HN posts on Google -indexed a matter of minutes or hours after they were created. Google knows the value of up-to-the minute information and I am sure they are working on solutions.