Prob would have a core number of people who would be interested, those being the ones who played Recettear and liked it. Any other interest would need more publicity. Word of mouth, facebook, steam, etc.
Depends on the (new) features and how well polished the game is, ie as bugfree as possible and a large variety of stuff to do. What works for this game is that it's pretty much the only one in it's genre, aside from some small flash games with similar but more simple mechanics. If it could expand this to appeal to the general public by expanding the amount of things to do, a more challenging goal, multiple ways to go through the game, a system that let's the player feel his decisions have an impact on his game, ... These things aren't that easy to implement, but if it could be done it would be a major hit for sure.