Our Khajiit just experienced an attack by an Ancient Dragon inside Whiterun. It occurred well after he had completed the main quest and started with the dragon attacking with shouts from outside the city walls. The dragon then flew into Whiterun, landing on top of Jarrvaskr. It then flew to Dragonsreach and landed in the front courtyard where it was finally killed.
Three guards were killed in the attack. All the Companions that were outside of Jarrcaskr joined in the fight, but none were killed.
Our theory is that Odanviing's entry into Dragonsreach unlocked the area for entry by other dragons, which had not attacked Whiterun proper before. (We had experienced dragon attacks at the College at Winterhold as well as Solitude, but not at the other major holds, the nearest being attacks on the docks at Riften and Windhelm.)
Please share any insights you may have. Thanks