Currently we have no scheduled date for the pre-patch, as Blizzard has not released a date or an end-of-season arena warning. However, they did send out emails earlier today warning players that time was running out to acquire various BFA mounts and achievements. It’s hard to predict when the pre-patch could hit based on the background downloader, as the schedule was all over the place in BFA: 8.0 prepatch data started three weeks in advance, while 8.1.5 data was a week in advance.
Recently, we compared the durations of past Warcraft pre-patches and most are only four weeks long, so we could be seeing the Shadowlands pre-patch on September 29th.
What to do Before ShadowlandsWhat Is Coming in the Pre-Patch
Players with Shadowlands PTR or beta installed shouldn’t have a large download, roughly 370MB, as the installation shares data between PTR/beta and retail clients.