Here's what I think.
Diablo I was ported to consoles. Diablo II never was probably due to issues with complicated controls, etc. Because of this Blizzard over the years has likely lost sales in the hundreds of millions of dollars if not more. I'm quite sure that they're aware of this. Painfully so.
So, time to think about designing a releasable version of Diablo III. It doesn't take much imagination--none really--to imagine that when design meetings were started for D3, someone named Morhaime or Pardo raised their hand, brought this topic up and said something like "Let's not make this mistake a second time. Blizzard, after all, has been a console game provider for much of its history. We should get back to that. Build the best game you can but let's not put something into D3 that will keep it from being available at some future point on multiple platforms."
And there you are. Maybe you think this is terrible; maybe you think it just makes sense. Limitations are put onto designs all the time. Whether or not this actually happened is impossible to say but it's certainly possible.
---------- Post added 2013-02-21 at 02:33 PM ----------
It very likely will be. They had job listings for a D3 Console Game Developer long before the game was even released. As well, if you hunt around you can find an interview from 2011 (I think) with someone from Blizzard where they speak briefly about putting together a development team for the console version. Things change but I'm guessing that Blizzard will keep this inhouse.
---------- Post added 2013-02-21 at 02:38 PM ----------
It's a slam dunk that it will make money. Development costs relatively are nothing at all compared to what they dumped into it over 10 years for the PC version. It will easily sell a couple of million copies and probably make back its costs during the first week if not the first day. It won't likely sell 10 million copies or anything stupidly huge like that but it will do well enough. There were plenty of reviews around about the PC version, not to mention terrible word-of-mouth, when they announced that they had hit around nine million units in sales and they still sold another three million plus after that.
This will likely be the easiest money they'll make all year.