One has to understand that Blizzard does NOT make games to be niche markets. They want to make powerhouses: Diablo, Warcraft, Starcraft. They're not some small newcomer to the market. Now, granted, they perhaps didn't expect the game to hit 10M, but trust me, they weren't expecting it to linger around 1 or 2M, either. Otherwise it wouldn't even make it past the drawing board.
Precisely. And now, you have a lot of those options, and they can offer more "fun per hour" and most important, more flexibility.
For example, I no longer can afford raiding for 4 hours in one sitting (because work and stuff, you know). I don't play MOBAs because the concentration of retards there is bordering on indecency, but for some people, it's not a problem.
If WoW becomes a niche market, you'll have about 5 times less content than today. A subscription-based, theme park MMO cannot be niche, because you have to endlessly churn out new content to keep people subbed. And you need a lot of resources for that.
Please stop linking videos from some Internet guru and use your own brain. It's a great feeling