It's more than a handful of people. This game sold well because it had a massive marketing campaign behind it. If it were a better game, I guarantee it would be doing much better than 6M. The number is still impressive though, which means there is some chance of another mainline FF game.
Also those improvements won't really matter much to the 6 million people who have already purchased the game. Some of those enhancements are probably still at least 6 months out.