I recently found this game and have gotten pretty addicted. I know you've said several times that you hadn't anticipated people playing for such long sessions, and so didn't plan much late-game content, but I had a few suggestions for some. I apologize in advance if these are repeats of other people's contributions.
I think it would be interesting to see more long term effects for repeated decisions, such as if you make choices that result in the sacrifice of your subjects, perhaps something of an uprising? If you refuse the sea monster often enough, perhaps the fishermen stand with you to fight it? I think some more unexpected consequences would be interesting to see as well. Like, occasionally if you let Granny keep her soup shop money, she pays it forward and gives out free soup, leading to more random happy points? Or, giving Little Timmy his coin will randomly result in him investing it in a lemonade stand that ends up making a good chunk of money and he pays you back?
Also, when your treasury balance is in the red, I think it would be cool if characters that you've helped several times (Granny, the Blacksmith, Pancake, etc) would show up from time to time to just help you out. Also, it would be nice if events that normally occured that would just give you gold like the candy tax, or profits from the Blacksmith or Granny's soup shop still showed up during negative balance situations instead of being stuck with only trading citizens or happiness for money.
I know people have mentioned expanding on some of the character's stories. I would personally love to see more going on with Pancake, or the Mouse, or Yet Yet.
Anyway, that's just a few thoughts I had. Thanks for your time!