I am just imagining 4 years from now, and all I see in cyrodiil is grand overlords.
That would be almost true already. Except very little people played just 1-3 characters since ESO started and stayed till now. I can almost guarantee you than in 4 years most of current PVP community will be replaced by new people. Even more so if PVP after 4 years will be same as now
(Obviously more frequent AP events and buffs to AP gain could speed it up and therefore greatly increase amount of overlords playing)