Once upon a time (back when the Run-Ons were there) there were three National weekends a year at Road Atlanta. In my time on the AR Board (started in the mid-90's) we used to have a drivers' school, two single SARRC weekends, a Double SARRC (Labor Day weekend), two National weekends, a Solo I weekend, and (starting in 1994) the ARRC.
The Solo I and drivers' school went away because the track wanted us to host only spectator events (and paid the extra insurance cost) to add value to their season ticket package - Solo I and schools ain't great on spectator appeal. A couple of years later AMA took over the Labor Day weekend and, after trying a couple of different venues, that event has now found what looks to be a permanent home at Barber. The February single SARRC was cancelled two years running due to track construction issues, then we dropped it completely after the 2009 event had 64 cars show up. In 2009 we also turned the July event into a Double SARRC, so we now host two National weekends (and March 2011 will be a Double National), the July double SARRC, and the ARRC. There are no other weekends currently open on Road Atlanta's schedule and I've been told they turn away 2-3 inquiries a week.
Road Atlanta is indeed one of the premier tracks in the US, we have an excellent relationship with track management, and I don't anticipate Atlanta Region will reduce our events there any further. That said, AMP gives us the opportunity to bring back Driver's Schools and Time Trial weekends in addition to adding new weekends to our race program. They are also appealing more to the karting and motorcycle crowd (limited concrete), so the overall impact on Road Atlanta should be minimal.
YMMV...