Different difficulty modes does not equate to content in my eyes, otherwise you may as well be playing Devil May Cry for the rest of your life since most games in the series have like 7 difficulty modes.
I am pleased with the amount of raid content they're putting out, I just wish Blizzard would actually give us more to do as far as 5 man content goes. Challenge modes and Heroic modes are not enough IMO, all they do is put us through the same environments and bosses with a slightly different spin. I want to see new locales, new enemies, etc.. You know, like most games that you pay for.
Let's look at what we got in expansions at launch in the past:
http://www.wowpedia.org/The_Burning_...ances_by_level
15 at launch for BC, all with Heroic modes.
Now let's look at WotLK:
http://www.wowpedia.org/Wrath_of_the...ances_by_level
Not as many, but still more than MoP.
It's obvious that 5 man content is not Blizzard's focus with MoP, but 7 new dungeons is still disappointingly low. I can tell you right now, players love their 5 mans. And Bliz is going to lose even more subscribers (I'm going to go ahead and predict another 2 million dropped by the end of this year) due to other competition and players getting bored with running the same 5 mans over and over.