simosaurus
CAGiversary!
Chubby, it sounds like you have already built up another nice little sequel in your head. Let's plug you into an HDMI cable and see how that all plays out. 
My first choice for ME4 would be the story of the First Contact War. I think that even though we know the outcome, there is a lot of potential material to mine there. We could be given the option to play it through as a human and then a second playthrough as Turians, Asari or Salarians to get the Council POV on the conflict. Plenty of options there. The thing is, this all seems like one, stand alone game, and not a new trilogy.
As for delving into the future and "What's next?" in the post-Sheppard universe, I don't have any big ideas. However, I'm sure that the big brains over at Bioware could come up with something down the road.
My first choice for ME4 would be the story of the First Contact War. I think that even though we know the outcome, there is a lot of potential material to mine there. We could be given the option to play it through as a human and then a second playthrough as Turians, Asari or Salarians to get the Council POV on the conflict. Plenty of options there. The thing is, this all seems like one, stand alone game, and not a new trilogy.
As for delving into the future and "What's next?" in the post-Sheppard universe, I don't have any big ideas. However, I'm sure that the big brains over at Bioware could come up with something down the road.