I honestly have no good answer for that...
Perhaps it's a hint that more about Shepard is coming. The kid does ask for another story about "the Shepard". I know it's grasping at straws (or emergency induction ports), but I'm still hoping something happens with the endings.
And it isn't that special, anyone that imports from ME2 will see it. I think the winter planet is supposed to be part of the current ending.
Also, that cinematic could be used at the end of the DLC endings too, it is ambiguous enough that it could just be how they prop open the door for future games in the ME Universe.