You'd be better off coming back in around 20 years if you want to see that, I think sex with Dylan will probably be right towards the end of the game. She'll probably have sex with Sam before she does anything with Dylan and even that's still going to be years away
Logically, i hope that in the new update Sophia will "help" Ellie with her hand, then she has to do it with Sam. Well, since this is no longer particularly taboo for her, she will be able to jerk off to other characters such as Aiden, etc., and so on in a circle.
Then she will suck Dylan, then lick Ellie, and so on and on and on, well - you understand what i mean - this is a vicious circle that lasts for decades! xdd