First, let's be realistic about something. Finishing in "first, second, or third place" is a fanboy metric. In business, you're not really judging your product from the release date of your competitor's product but from its own release date. You'll be looking at things like sales rate and market share first. You won't see a restaurant go "OMG that other restaurant opened before mine, they've already sold a million more hamburgers!" I know fansites will never get over this infatuation with "winning" a generation but for a serious discussion it needs to be put aside. When I opened my first business all I was really concerned about was if the market would bear another of the same type and how much share I could take.
Sony, provided they avoid the disaster of the PS3's launch, could release last and still do quite well. I think this generation has proven that. Even with all the hiccups, Playstation is still the second strongest brand globally. The PS3 is going to outsell the 360 by a comfortable margin this year, even with Microsoft releasing Halo 4 and a Forza title and the PS3 having no high-level exclusives, and next year will likely be more of the same. I think it's safe to say that fans of Sony games will wait for their console to launch, just like fans of Halo or Gears will wait.
Now, that being said, I think both Microsoft and Sony need to launch within 6 months of one another. This would allow them to advertise their own console release simultaneously with the launch of the competitor's console. If you're a fan of X brand and you know it's coming soon then you'll probably be able to hold off.
I predict the PS4 will launch in January of 2014. That gives them a shot at the Japanese New Year's money and Christmas money/gift cards in the west.
