In the last couple months we've been driving efforts to bring Drupal's core aggregator up to speed so that we could use it to replace FeedAPI in Drupal 7. After trying to pull through some of the more extensive changes, I have to recognize that in this case the advantages of Drupal core work are not enough to outweigh the disadvantages.
While there was a real need for the update, the support just didn't seem to be there and development of the update slowed to a crawl. Alex notes that the original goals for the FeedAPI updates need to be rethought - don't replace the FeedAPI component, make a true successor instead. There's plenty of comments and thoughts from other Drupal-ers on the post, so read up!