There's one less cracky, terrible possibility, and that is that he's there to see the fireworks which are also for Suzaku, so as to finish up his one and only plot-line in the show. I doubt it though, as its inexplicable since at the end he had come to hate both Suzaku and Lelouch.
The more you think about it, the less sense he makes there.
To the best of my knowledge nothing has been said about Gino at all. The only thing that I know that was said was that Gino and Kallen were only comrades in arms, in one FAQ-thing in a magazine. That's pretty much it, his character has been completely void from post season materials.
Surely you jest, it is but the epitome of sense and viable conclusions!
I am already worried that this last PD will be a stupid plot hole. If the truth hasn't been revealed (which becomes a plot hole due to Gino) then it amounts to the SC going like "Hey Gino! hey Zero and Queen! Fancy meeting you here!" To be honest, though, this last PD seems like its just an attempt to cram the characters together, because in all honesty Gino makes no sense in there given who else is there.