Everybody look, if the rest of the Elder Scrolls games were just set in a 'dark age' the setting of the series would get quite old wouldn't it ?
*EPICFACEPALM*
This is what TES is!!!
It won't get old, if they changed it, it wouldn't be TES!
It's never been set in a "Dark age". Its always had a medieval setting, always will. Skyrim has been suggested to have a "dark age" setting in a correlation between real world historical events, and the events taking place in Tamerial at present.
Its lasted what, twenty years, in it current guise. I think its quiet safe.