It's definitely possible. It's important to note that they're giving lifetime sales expectations, which is factoring in 25-50% off sales that will happen over the months/years after the game's been released. I can totally see them coming close to that number. They're giving it such a huge push what with getting Aaron Paul, Lena Heady, and Sean Bean to star in the CGI movie, and the apparent resurgence in "mainstream" popularity of anime thanks to Netflix/Crunchyroll/Hulu (I'm just making a guess due to the prominent placement anime gets on those sites, and the popularity of anime conventions, not completely sure if a "resurgence" is true). This game is anime as fuck, but the FF franchise also crosses over into the mainstream the way few other anime-as-fuck franchises are able to (I think pretty much just DBZ and Sailor Moon do it to the same degree).
I can totally see the potential for the game to sell 10-12 million over a few years. With the huge crossmedia marketing push, the thirst for a good post-FF12 console FF game, it being pretty much the first mainline giant JRPG franchise on next gen aside from Zestiria (which is much more niche than FF), I think it has a decent chance of hitting their goal. Especially if its reviews settle somewhere between Xenoblade and Xenoblade Chronicles X.
Agree that PC has a ceiling of about 1-1.2 million based on sales of FF13/other JRPGs on Steam. Xbone I think will sell closer to 1.5 million, so they'll need to get close to 8 million on PS4. I'm expecting lots of bundling, probably some sort of patch/promotion bundle with the PS4K (maybe retrofit the advanced graphics options from the PC version to the PS4K version?), etc. Again, over a few years, I can totally see it being possible, but the game will need to have a really great debut and really long legs.