Even with the eyes reappearing, I doubt they're going to bring Nidhogg back. The cutscene after Final Steps of Faith made it pretty clear that his vengeful spirit had at last been put to rest.

So what I hope doesn't happen, is that Griffon winds up using the eye's raw power to betray the Ascians. ie: EXACTLY WHAT THORDAN DID.
If that were revisited, I'd definitely call it laziness.