At any rate, I don't see more than two Dragon Slayers in Sabretooth right now, because they were named "the double dragons". I'd say if the translation is accurate, then it's a hint that there's only the two of them.
And I also don't think the dragons returned at all, because it was mentioned that nearly nothing had happened during these seven years and that it's been awfully quiet. I think something as big as the dragons returning would have been mentioned otherwise. I don't really see them discarding it as "nothing".
Well, anyways, we'll probably know more in a few weeks