I only log on for an hour a day, sometimes two, and only raid twice a week. My guild just cleared heroic ToS with no participation requirements. We are what I would picture as being casually serious. We aren't even close to cutting edge and I feel no desire to endlessly grind like some feel the game "forces" them to. With the changes coming in 7.3 the expansion is a lot more alt friendly and I'll probably spend more time logged in while leveling each class. I am loving the game right now, feel like it's got something for me even if I've only got 30 minutes to log in and play.
OT - I would not be surprised to see highlights of the next expansion at Gamescom, with either an alpha or beta opening at Blizzcon or right after it.