Re: The Curator.... Who is he? (SPOILERS for "The Day of the Doctor")
Essentially, he's Moffat's version of the Woman in White from The End of Time. The Woman, of course was intended by RTD to be the Doctor's mother but her identity wasn't stated on screen so that she could be whoever the fans wanted her to be.
I thought she was Susan. Put photos of them side by side, you'll see why.
As to Baker, a later (but not final) regeneration, going back to an old favourite face. And yes, they don't need to do any more than that, leave it there.
"Ö Times change, and so must IÖ we all change. When you think about it, we are all different people, all through our lives and thatís okay, thatís good! You've gotta keep moving, so long as you remember all the people that you used to be."