Well, Phil Collins is officially back so I think there's a fair chance he might reunite with Banks and Rutherford. More than a fair chance actually unless his health won't allow it. The Problem here is convincing Hackett (Who's been fine with his solo career and is upset over their latest documentary on which he thought spotlighted specific members more than others) and harder yet bringing Gabriel along.
Buuut from what I've gathered from interviews and such, they seem open to it, so there's always a possibility of at least one of them getting up on stage and playing a couple of songs, you know. A full reunion with a full set? I'd agree it's unlikely. That would mean Collins would have to go back to the drums and he himself said he's not sure he can handle it anymore.
It's unfortunate, seeing as Gabriel paved the way in everything he did for whatever became Genesis past 74'. Musically/lyrically it was too rich, easily the best era imo.