One would wish that it would be Star Wars Weekends as that would be really neat to announce something like that during one of those events.
It wouldn't surprise me if more of Disney Springs and all of the changes to Animal Kingdom will be announced at D23. The new Frozen changes at the Norway Pavilion might also be given a mention there.
The DHS rumors have been pretty strong as of late. And the shutting down of attractions, along with moving the Frozen Singalong and the new flex theater that is going to be built between ToT and RnRC, all point to something on the horizon. Also, I have, as of now, read from several different sources that the Echo Lake area of DHS is going to be going away soon. There is definitely something brewing. It is unfortunate that it has to be at Disney's epically slow pace.