That's a good setup for a continuation. I hope there IS a continuation. Also, the size difference between them is inconsistent between scenes. His height was up to her breasts when they were standing next to each other, but he shrank to nearly the diameter of one of her thighs during the sex scene, then he's back up to boob height for the end.
This work is amazing. Both the plot and character design are on point. It's an excellent piece. The only minor flaw is that the author's drawing skills aren't very strong. Otherwise, it would definitely be a top-notch work in this genre