The latest dev release has support for rich notifications which will support Now cardsGoogle is moving fast with the Now integration into Chrome, it's now laying the groundwork with a new style of rich notifications which will eventually contain Google Now cards.
The latest dev channel release comes with rich notifications support, though the feature is hidden behind a flag ("Enable rich notifications") and only works on Windows and Chrome OS.
While everyone is excited about what Google could do with Now in Chrome, the new rich notifications go beyond that.
Google is putting together an API available to all extensions and apps, which would make it possible to notify users of status updates, incoming emails, appointments and so on.
There's already a notification API, but it's based on an outdated W3C spec and it's not very flexible. With the new rich notifications API, apps have greater freedom with the look and feel of the notifications.
That said, one of the big reasons behind the API is to add Now cards, there's no ambiguity about that. François Beaufort was able to get ahold of a screenshot of what the rich notifications look like in action.
Google is still trying to assess the impact, on performance and other aspects, of building Now into Chrome, but there's no question that it's coming.