I've been viewing this as a 4-6 million product (for the first year) with potential upside.Do you have a personal guess? I'm curious, as you're always good at analyzing this stuff.
If they're primarily just appealing to existing fans, I'd probably expect it to run out of steam around 6 million units by next Fall (barring some kind of re-release or port). FFXIII was incredibly front loaded compared to other major RPGs last gen for example. Mass Effect 2 started around 600K while FFXIII started around 1.3 million in NPD, but they both ended around 1.7 million last I saw. Even things like Skyrim or Fallout, which had huge upfront sales, had curves more like Mass Effect.
If they can retain most of their fan base and get some new people, they have a shot of getting to 7-8 million and matching FFXIII, which I think they could view as a strong success.
Japan will be down around a million copies versus FFXIII, so they need to make up a fair amount of ground overseas.