Google has applied for a patent for something that sounds an awful lot like Facebook's ticker feature. While we can only speculate on Google's plans, it seems likely that they're thinking about a similar kind of functionality on Google+. And why not?
Bill Slawski at SEO By The Sea points to the patent filing for "Social Discovery of User Activity for Media Content". Here's the abstract:
Apects of the present disclosure provide techniques that may enable user activity information to be automatically generated and shared with other users of a social network. In one example, a method of automatically publishing, to one or more social network services, information about user activities regarding media content items includes receiving user activity information regarding a media content item, wherein a user is a member of one or more social network services, and the user activity information is generated in response to one or more activities taken by the user with respect to the media content item.
The method may also include receiving an indication of one or more users of the one or more social network services to whom the user activity information is to be made accessible, and automatically publishing the user activity information to the one or more social network services.
So, it sounds like you would see a lot more activity from Google+ users showing up in a feed than just the standard stream of updates you see today. Again, we can only speculate, but the Facebook-style separate feed (separate from the News Feed, that is) style would make more sense than a total replacement. This could appear off to the side, or simply as another option from a drop-down for the main stream.
Facebook itself, of course, is rolling out some design changes of its own. Interestingly, these seem to essentially kill off the ticker, or at least de-emphasize it a great deal.
You can read the full patent here.