I don't think the WT Q&A will disappear any time soon. It's not a discussion or debate it is simply reciting the published answers.
However, the CO visit has changed over the years. He used to give 4 talks, now down to 3 and none of them have any audience participation. The older ones on here will remember the CO visit on Saturday evening "new things learned" which was questions on the previous 6 months WT's. He wouldn't take QA's in his Public Talk but would involve the audience in the other two.
Some may also remember the late DO David Carter who would even take answers from the audience at a Circuit Assembly.
George