You can filter down to Object and Views in a content pack XOG or content package, but there's not an option available for adding Attributes alone.
So when you XOG the Object it will bring across all of the attributes (barring some stock attributes for stock objects, which can exclude themselves), including new and old.
Edit: Unless... after adding the object to the content package, you then use the Hierarchy page to drill down into the Object and then exclude any attributes you don't want to include. That is covered in the article link. Sorry, I spoke to soon this time.