If the OGB plays any Role in Future BioWare Games, I think it will turn out that it actually isn't quite as game-changingly significant as it could be expected.
Given that we know so little about the old Gods, much less what makes up their "Soul", I think the OGB will turn out to actually be just a very broody Child - maybe with great magical Talent, given it's Mother (I don't think Souls give someone magical Talent, at least not in my Theory) - or, worse, a Child that would come off to others as "retarded" (I do not mean that in any insulting Way), as it has the Soul of a Dragon, which might not be on par with a human Soul...
Anyways, having the Baby not be significant in a gamechanging Way is probably the only Way it will EVER play a Role in a Game.
But, it has a positive Side, before I'm thrown amidst the Sharks: It would make the Dark Ritual actually a much happier Ending.