Well did you read what the original ending was supposed to be like? Drew Karpyshyn had already planned how it would end and Mass Effect 2 contains some stuff pointing in the that direction. Shame they opted not to use it as it would've been a better ending.
But yes the lack of closure is the what's bothering me the most too.
It's not confirmed yet but much is pointing in that direction. Stay tuned!![]()
That's because ME1 and 2 didn't have one. Multiplayer is new to ME3.