I think from looking at IMDB and seeing that Electro has been cast as has Rhino, I can't help but feel that for this film series they are building towards the sinister six or a variation of it. Like you I'm also intrigued to see how the new MJ and Harry fit into the series. I'm guessing MJ will be introduced as the new girl who moves in next door. Harry i'm guessing will be a new pupil at Midtown high after being kicked out of private school (kinda copied the idea from the original film) as it would make sense. I have read Harry will be a long term friend of Peter's who has returned, so it will be interesting to see that. I'm also wondering if Gwen Stacy will die in this film or in the film series at all.