Don't think a general thread of sort for this convention has been made (including before), so why not.
D23 expo is the Ultimate Disney Fan Event that is biannual at the Anaheim Convention Center (which is near California Disney Parks), and with the last one being in 2015, now it is coming around again this weekend from July 14th to 16th. Expect the many aspects of the Disney industry to be there, and there is quite a bit.
Who is planning to go, and what do you want to see? Here is the Schedule and Guide App to help out.
Schedule
App: iTunes/Google Play