User blog comment:B214/Chapter 510: Natsu's Heart/@comment-7418318-20161114111629/@comment-30338537-20161114175444

There won't be another DS, as Acno already listed all eight (Natsu, Gajeel, Wendy, Sting, Rogue, Laxus, Cobra and Serena). If there was another, he would've sensed that DS.

That child likely refers to Natsu.