It's okay, lostraven, I'll take this one.
Will there be sex with Mary, or will we need to wait for another update?
Usually in incest games, the familymembers are the main targets, while the others are (by lack of better word) "filler" (not that I have a problem with that, mind you, I remember being very disappointed in another game when a "filler character" was cut because the audience was too focussed on the family, and it also didn't help that it actually was the only "filler"). So, as you might expect, the main story will gravitate towards this relationship and will (understandably) be the hardest to achieve, so it will take the longest to implement. It also makes more sense to put in the "side quests" and "filler characters" before you finish the main quest. After all, if you finish the main arc, why would you keep playing? I know a lot of people mistake this with "milking", but this only applies when there's really no progress at all and there's nothing else added to divert your attention. And in Taffy Tales, there's enough to keep you occupied.
So, TLDR: No... no, there will be not.