I am much in the same camp as you are. Drawing from the lead up events as you did my imagination paints a similar picture:
Second to the last event of the day. Dylan and Sophia finally get to use the hot tub (in spite of hot San Alejo weather). While in the hot tub Dylan offers a nice shoulder massage which Sophia accepts. Dylan makes some comment about the bikini top straps preventing him from performing a proper job (Sophia decision for filthy and Dylan points). Dylan uses the unhook skill that Sophia taught him and the top come partially or completely off. Then, after Sophia begins moaning in pleasure to Dylan's talented hands Dylan makes the Zac move towards Sophia's breasts. There is no Alyssa interruption (Sophia decision to let Dylan proceed), and Dylan massages Sophia's breasts. This time it is willing as opposed to the foreshadowing forceful event with Aiden. Since Sophia is a tactile creature as seen by sensitive nipples, her reaction to Sam's caress on her arms, her reaction to Aiden's squeezing and phallus pressing during the art class scene, Sophia's excitement when the breeze fluttered over her braless breasts in the classroom...Sophia is now enraptured.
Sophia is now thinking a lot less about Dylan's lineal heritage and more about his linear profile. Dylan senses this and goes in for the kiss (Sophia decision
critical for the last scene).
If Sophia gives Dylan a deep romantic kiss then they move on the last scene in which Sophia reprises her posture as with the Hoplite Boys. The culmination is achieved either manually or orally depending on decisions made by Sophia.
If Sophia does not return Dylan's kiss in the hot tub, then She and Dylan spend the last event playing video games in Dylan's room.
This scene is probably a year away, and all the pulling from previous foreshadowing we are doing gives no guarantees that the reality remotely resembles or imaginings. However, I believe this would be a fine and reasonable possibility to end the next day.
Thank you for your thoughts, and thank Bane71 for initiating this interesting conjecture.