Well I think FF XIII will likely be the lowest selling Final Fantasy game in years (that is if it even gets released on PS3 and isn't canned / transferred to another console in the meantime).
Don't forget that hardware sales affect software sales - why do you think the same game sold 5 times better on PS2 than Gamecube? Because it had a userbase 5 times as big. Games on Dreamcast that would have been massive on PS and even N64 sold pretty poorly due to the hardware userbase.
It's a complex effect. The games to an extent will sell hardware but the hardware also sells games. If hardware sales stay at sub 10k all year than many projects will be canned. Publishers / developers are, after all, businesses and exist to make money. If they need to get out and cut losses they will.
If, for example, PS3 sales were to hit 2 million by the end of the year (actually quite optimistic) and say there is a price drop in the new year so weekly sales go up to 15k per week and FF XIII comes out in March, do you seriously expect it to sell 2m at launch like past installments? That would either mean every single PS3 owner would buy it or it would sell a 100,000-200,000 per week for a while after launch. It's not going to happen. Sure a game like FFXIII will boost sales but not by that kind of an amount - you have to be realistic here. At the same point Wii sales are likely to be 5-6 million so wouldn't it make more sense for future SE projects (KH III, DQ X etc) to then come to Wii where they will cost less to make and sell more?
