I wanted to talk this because we have never really discussed this. There have been a couple FanFics about this, but other wise, nothing. Of course this is all going to be speculation, but I want all the opinions you've got. EVERYTHING!!! *grins sheepishly* :-) Anyway, toss anything you got at me!
^^ I really like @Riverglade's theory about there possible being another herd of wild pegasi in the realm. I can see that being a REALLY interesting story arch that would bring a whole new layer of complexity to the whole series.
Oh. My. Goodness.
Personally, I think that the Lake Herd steeds that escaped captivity formed a herd when they first came over during the first reign of Nightwing. And then Storm Herd finds them on their way the lands Redfire found.
Idea 1. Probability: Very Unlikely.
Storm Herd lives happily ever after.