When the first rendering below came out, I thought for a moment it was a futuristic castle rising out of a fairytale castle, ala Voltron. That would have been be very bold, cool and too high-concept for Disney to risk doing. The starry sky, long windows and laser-water helped give that impression.
The above rendering makes the buttresses look flat. We need a physical model or 3-d rendering to see how the five or six flying buttresses spiral up and around the main tower. That will be a cool aspect.
As we've all noted, the make-or-break factor will be if in the end it looks like an awkward giant add-on or a naturally integrated landmark castle: materials, colors and style of the towers will all play into it.