ambam :
Are you absolutely sure of this? Can you provide a link?
I'm not absolutely, 100% sure, as I have yet to see a blue post about it on the battle.net forums, but the general consensus amongst all players has been and continues to be that because Diablo 3 is not an MMORPG it will not be set up on a pay-per-month basis. Starcraft 2 recently came out and only required a one time payment, free per month, and it didn't even have something like Diablo 3's real money auction house (RMAH).
What most people are arguing right now is that for Diablo 3, with its ingenious RMAH system, and the significant fees they will be taking ($1.00 off of every RMAH transaction, and 15% of your money if you want to transfer it from your battle.net account to a PayPal account, of course you can keep the 15% if you want to use all that RMAH profit to purchase Blizzard products in which case they take 100% of it...) they have found a way to make more money than they ever would from simply monthly payments. Those who can't pay won't have to, and those who can pay will be able to dump as much money as they actually can into the game on a monthly basis rather than just being limited to that $15 a month payment. Even better, those who can't pay will be able to sell to those who do, and that money they make will likely go back into RMAH purchases. So if someone invests $30, as that money is traded through the RMAH, after 30 transactions all that money belongs to Blizzard. Assuming most people will keep their RMAH profit for RMAH purchases, this leaves Blizzard with more profit than I imagine any $15 monthly payment system could hope to offer them. Since those who can't pay $15 a month will still be able to use the RMAH system starting as sellers rather than buyers, they help to push this system along by adding transactions to the system. So even though they technically can't pay monthly, they still end up turning Blizzard a profit without directly investing a dime. To couple this with a monthly payment system would likely be seen by players as a complete outrage, and would have a lot of players up in arms. It would be a huge wad of spit from Blizzard into the faces of all those faithful Diablo fans who have been waiting since Diablo II and have expected all along, with no information claiming otherwise, that the game will be free to pay monthly. If SC2 can afford to be free monthly, so can D3, especially with its RMAH. I don't think Blizzard will need that money for server sustenance or anything like that, and making the game pay to play probably stands to lose them money in the long run seeing as the more players participating in the RMAH, the more transactions there are back and forth, and the more they profit.
As for a link, according to
this article, some regions may have a pay to play model as it is for whatever reason preferred in their area, but North America is not one of those regions. Apparently confirmed by "sources at Blizzard".