Nobody can answer that, and L&P never said a word about Sophia being part of those sex-scenes either. He just said it involves important characters. Also, when L&P made that statement, he said the first lesbian sex scene is scheduled to happen within the next 3 playable days. This statement was made during PD12, so you can expect it to happen on PD15's ranch event or whatever else he's planned for that day. At current pace that's up to 5-6 years away, depending on the time of day (which update) on PD15. The first hetero sex scene is expected to happen on PD16, so it could potentially be 8-9 years away at current pace.
Mind you these estimates are highly inaccurate as L&P's development time has always been going in one direction, and one direction only. Hint: It's the opposite of faster. But incase of a miracle happening, it could technically be slightly less time. I wouldn't bet on it tho.
My personal guess? The lesbian scene involves Alyssa and another woman at the ranch we don't know yet. As for the hetero scene, my guess would be Dylan with one of the many girls he's "recently" getting it on with (not Sophia), or Ellie and Logan.
Edit: Okay so, I was wrong about the people involved. Atleast in parts... L&P apparently said that these sex scenes involve Sophia, Ellie and Dylan. But what exactly that means is to be seen. Sophia could just happen to witness sex involving the other two with god knows who. Anyway... Hard to say if we'll ever get there.
