Well, will try to keep this short (ha ha). I've seen so many threads and posts saying silly things like "oh wow if Diablo 3 Inferno is beaten before the end of 2012 it's too easy". Some people claim to want this game to be harder than anything so far. We've just had a pretty big thread with some guy adamantly claiming that the game *won't* be beaten by the end of the year.
I say: horsefeathers. And more than this - no one in their right mind actually *wants* this to be the case.
This is why I believe this.
Some people are just really good at videogames. Whether it's a skill or a product of them having a lot of spare time: it's just the way it is.
This is very common in Asia and you see some games designed to deliberately appeal to guys like this. Dark Souls is one of the more mainstream ones. Give Touhou and Mushihime a look too. I've personally seen some guy beat Touhou on the hardest setting at a local arcade, on one play.
In the West, probably the hardest legitimate game (that is good) is World Of Warcraft - Heroic Raiding. Say what you want about WoW, Heroic Ragnaros, Mimiron, Yogg0, Lich King, Sinestra, Nefarion and others are pretty damn difficult - too hard (prenerf) for almost everyone.
And yet guilds like Paragon routinely kill them within 2 or 3 weeks.
With gamers like this out there - Diablo 3 will be beaten within amonth or two, and most of this delay will be about gearing. If they don't, there is some sort of roosterblock in place or this game is overtuned.
Just because they can do it, however, doesn't mean that many others will.
2) Hard = Good. Impossible = Bad.
From the above, to make a game that even the top 10% can't beat more than likely means overtuning it to the extent that it becomes nearly impossible. We've seen some fights try this in WoW - Mu'ru is one that comes to mind.
The problem with this is it creates a scenario that just isn't fun and becomes more about RNG and banging your head against it until the law of averages lets you through.
Blizzard isn't stupid. They may make Inferno hard as nails and out of reach for the average player without a significant amount of gearing and practice, but I'm sure they know that *some* players are going to be good enough to barrel through.
3) Extra Content.
So, what's the answer?
Pretty much to just stay ahead of the wave. I'm sure that every few months Blizzard will add some new content to the game. Not a full 'tier' as in WoW, but some new bosses or events that will push the top level of players to the limit.
At the end of the day, people need to relax. Inferno will be very very hard. Some people will still beat it.
However, it's not likely to be *you* :D.