Capcom hasn't exactly been known to make the most sound decisions as of late. I'm still trying to wrap my head around the inclusion of Bad Box Art Megaman to Street Fighter x Tekken, not just as a deliberate troll maneuver, but as a PS3 exclusive as well. But, some things they still have a bit of common sense on, if only a little.
While the company is still at work with one of their new IPs, Dragon A- er, Dragon's Dogma, they also have a new Resident Evil game that has suddenly popped up into the public eye. Of course, fans are anxious to know what exactly they're going to be doing with this newest edition to the RE franchise, and they want to help promote their new products as well. So, every retail copy of Dragon's Dogma will come with a free demo code for the upcoming Resident Evil 6.
Dragon's Dogma itself is set to come out in May, but the codes itself will be activated at different times. Xbox Live users will have the privilege of getting access to the demo first in July, while those on PSN will have to wait until September to be able to try it out. As for why the large discrepancy between the two console versions, that's anyone's guess, though it could be an attempt to gain additional favor in the west, since that's where the Xbox 360 has the most success.
As for a chance to get a demo without having to buy the game, that option doesn't seem to be in the cards for the moment, nor is it known if it ever will be. Then again, stranger things have happened, so they may very well be able to collect enough common sense for a general demo release.