Yea, unless Bethesda just decides to throw rationale out the window when deciding the future of Cyrodiil then a republic is not anywhere in the near future. The people are not used any republican forms of government and so aren't going to be quick to jump at any ideas of equal representation and the like, chances are it hasn't even crossed their minds. Given the extreme case that it does come about that there's a republic then, once again unless rationale is thrown out the window, it'll evolve into an oligarchy and thereby back into an Empire. The Elder Council is nothing close to a format for basing a republican government, so no matter how many roleplays turn the Council into a republican Senate, that's just not the way it is. The Imperial line has been broken many times before and pulled through it, I figure it will again; they just need the right person to come along and take the wheel...
I think when most people say "Republic" they mean oligarchy, which is very possible. Republic suggests "representation" which will not happen, but it is very real chance that the Elder Council will rule, not as representatives, but as oligarchs. The Council usually rules until that "right person" comes along. Heck, they usually rule even when there is an emporer.