People have been raising GOG and humble bundle as a potential source of extra sales, but whilst I'm sure the sales there aren't non-existent (otherwise they wouldn't bother), I highly doubt they'll be any more than a couple thousand for third. Steam IS the mainstream PC market and as such will be where most copies are bought, outside of a freak overlapping of fanbases between niche JRPGs and alternate storefronts.
EDIT: In terms of price vs getting people to actually play the games, I think it's a little of column A, a little of column B. The games now have turbo modes. Great. But do people really know that this exists? Let's take an extreme example.
You're an average steam user who bought FC whilst on sale a year ago or something. You either never played it, or played a little then got distracted by other games. You never got the achievement for beating the prologue, just like 62% of the game's audience. Would you keep the game installed? Would you have it installed to begin with? Possibly not. And if that's the case, you may never notice that the game's been updated with a turbo mode. Or if you did notice, would you look into just what that is? I won't say that the name doesn't describe it very well, but the average consumer may think that it's a new mode entirely, or something. And even then, a turbo mode is only a selling point to someone who's already playing the game, realistically. You'd still need them to get back into the game, for them to realise what a great feature turbo mode is. Otherwise it's a case of "Well I played 30 minutes of this game, but never went back to it, it can't have been *that* spectacular. I doubt a turbo mode could fix whatever problems I had with the game".
But then of course, the upside of this sort of consumer is that they blindly bought FC without considering if the game was for them. They could very easily do the same for the rest of the series without finishing it, promising themselves that they'll get around to the series some day. But for that, they need to see the games, and for whatever reason be tempted. Maybe it's a low base price, maybe it's a low price as a result of a sale, maybe the sale percentage is just *so* outrageous that the price doesn't matter, maybe there's a trilogy pack that offers them a discount thanks to owning FC, I dunno. The amount of people actually playing the third could be close to zero, but if xseed sold 100,000 copies at a decent price, I doubt they'd care financially. The problem is just what the consider a decent price. (A $10 game needs to sell 3 times the copies of a $30 one, after all.)
