I mean, let's run down the possibilities here:
1) It's true and Sony doesn't want to say anything yet, so they issued a denial.
2) It's not true but IGN was lead to believe it through usually credible sources that were themselves given wrong or incomplete information.
3) It's not true and IGN took very weak sources and ran with them irresponsibly.
The third one is a really, really heavy accusation and basically torpedoes them as a news source. It's possible, but would have had to be done damn near drunkenly for an editor to post it.
The second one seems the most likely to me. I don't really buy the "Sony was trying to root out leakers" theory, but I can easily see people just getting it wrong. If this is the case and IGN didn't knowingly put up a false story, they might be trying to find out where in the chain the information breakdown happened before they acknowledge it as false.