I don't know what you mean by game break repercussions for future games,after all in Morrowind we ended up as the Nerevar,a top figure close to Vivec in importance for Morrowind culture/people,and since every game they make its always on a different setting/area and quite some years after the previous one,what are the repercussions for us to end as a emperor?
I suggested that not meaning i would like it btw,that could be annoying to continue playing after the main quest is done,just that it seems to me a possible route for them to go with,or who knows,different endings.
First of all, you are not Nerevar in Morrowind. You are the Nerevarine, which is a reincarnation of that historic figure, and even that's debatable if you are truly him. Without Nerevar, the Tribunal (doesn't anymore as they were fake gods) wouldn't even exist and Vvardenfell would have fallen into darkness.
As far as being the emperor is concerned, how could BGS fit that into TES lore? There is no way a nord/argonian/orc/redguard/etc could be the emperor of the entire empire. Everyone's story, character, and choices would be completely different. The only way I could have seen that potentially being pulled off is if BGS forced us to play a specific pre-determined character, which isn't what they do. Which leads me to believe that the Dovahkiin will either get a fancy title with armor and be done with it, go on a journey like the Nerevarine, or become a daedric prince like in Oblivion. Something crazy like that as to not have previous characters conflict with future lore and games.