So, along with the bosses per tier poll. How many dungeons would you consider an acceptable total for an expansion to have? Think "less than this would make me unhappy".
Personally, I quite like the 5 mans until there completely stuffed full of folks without the time or patience to learn and wipe a little. If Blizz would go back towards the occasional epic 5-man (BRD... still makes me happy in my pants from around 49-56 when levelling an alt, try and talk people into staying if you know the place, it's amazing how few have seen it all).
Adding something mechanic wise with the scaling tech would be nice so you get random harder spawns as your groups ilvl average increases (and better loot as a result with the occasional "rare" mob with significantly better gear appearing as the groups gear level gets extreme).