The game will be connected with your save files from skyrim so if in skyrim you wipe out the stormcloaks they are non existent in TES 6. It could be set ALL over tamriel. Their could be a different main quest line for each country but they all fit together into one major main quest. Like for valenwood the main quest could be that valenwood has their own rebellion and the rebels drew courage form the stormcloaks and rebelled against whoever controls valenwood, it would be a bit like skyrims civil war quest but more diverse and with a deeper and more meaningful plot to it. The game should be set shortly after skyrim (maximum 2 years). Maybe an appearence from your previous character, as general tulius's or ulfric stormcloaks right hand man or second in command.
Anyone think this is a good plot? Feel free to post your own plot or improve on mine as this topic is for ideas for TES 6