User blog comment:Argorrath/Treyarch releases a BO2 teaser video called "Origins" for DLC 4/@comment-3967954-20130807171131/@comment-3967954-20130807175148

It's unlikely to be "the original characters but younger". The original crew would be really young during WWI, and almost certainly not fighting on the battlefield, and these new guys don't exactly look young themselves.