Embedded objects based on the html object tag are getting more rare these days. There are two things I see happening more regularly:

1. Applications embedded inside a document, e.g. MediaElement.js audio and video players. You can find at least two players on this page using the application role. I'm not sure whether this meets the accessibility standard, it's just that they seem to have implemented it this way. Other examples include rich text editors, which are in fact edit fields but they aren't accessible using quick nav. Since treating them as edit boxes will be quite difficult probably (you can't see whether an application is a richt text editor or not), I think object would be a nice alternative
2. Websites that have dialogs embedded on them. Usually, those dialogs should receive focus automatically, but they often don't, which requires you to find the dialog using browse mode. Quick nav for this is something I'd certainly use.