How great is it that, in 2 minutes, Tom Baker creates a second memorable character for this series? It also wasn't lost on me that he was the only classic Doc not to participate in the 20th anniversary and was the ONLY classic Doc in the 50th. The damage to the Vortex has been repaired.
I hadn't thought about the second part of your statement until just now, but there is no small irony in that. I suspect we'll never know for certain who he was meant to be, though personally, I like the idea that his is indeed the Doctor's final incarnation, and that he did retire to become 'The Curator' of this place.
Either way, it was both brilliant and touching, and I loved every second of it.