While I've seen nothing publicly on it yet, I have this from two sources. There has been a change in the Friday morning schedule for next week's Council Retreat. Friday morning will feature a joint meeting between the Virginia Beach City Council and the Virginia Beach School Board at the Sandler Center. The Retreat will continue afterwards for Council - as slated - in the Department of Economic Development (DED) Conference Room. The reason for the Sandler Center is that the DED Conference Room is too small for the joint meeting.
Both sources confirmed the Friday joint session, with the first source giving me the location. I'll update this post when (if?) I learn more.
Update 1: I have it from a third source that the Friday morning session is joint Council - School Board. However, the source - like the second - didn't know the location.
Update 2: I now have it from a second source: it's the Sandler Center on Friday morning.
Update 3: the City put out an official release Tuesday afternoon: Friday morning is at the Sandler Center, with the remainder at DED. You heard it here first.