What will happen is that it will be pre-filled with sites that are popular in your locale, organizations that Mozilla likes, and sponsored sites: http://cl.ly/image/3I172o2f202k
The pre-filled sites disappear and are replaced by your own top sites as you start using the browser.
currently the default new tab page on a NEW installation is mostly empty: http://i.imgur.com/z71I89i.jpg
What will happen is that it will be pre-filled with sites that are popular in your locale, organizations that Mozilla likes, and sponsored sites: http://cl.ly/image/3I172o2f202k
The pre-filled sites disappear and are replaced by your own top sites as you start using the browser.