When does the event lists get updated? I know that there are some games that were submitted but have not been added to the list yet. Is there a set timeframe for this process, for example, events submitted on Monday and uploaded to the database Thursday?
Late submissions can take up to 2 months (or more) to get approved; pretty much nothing gets done in 3 days.
The return & replace operations are not connected; you return the tickets you don't want now, and when the events you want go live, then buy the tickets.
You're best off refunding the tickets now, so you get full system credit for them. After June 16, they take a 5% handling fee. Also, if you return them before the 16th, you won't have to stand in the Customer Service line to refund them.
If you're not sure the new events will go live, and you're keeping your current events in case they don't, then you will have to wait, and possibly take the 5% & CS line hit.
I always use the eventDB to see changes http://gencon.eventdb.us/changeList.php