Chances for Max to return are really small. And even if he returns, no chance for him to be a trainer, because of main rule of Pokémon anime (see my sign).But I think (or hope) that Max is an exception...something tells me that Max might start his journey in Jhoto to promote the GSC re-makes? (Assuming that they are in production?)
And there are also no chances for GSC remake. Not only is no reason for it, because you can already get all Pokémon in DP, but also if they planned it, we already knows that.