The next Overwatch patch is such a patch where according to Blizzard, it seems that the patch will be so big that it will basically require a reinstallation of the game. According to Blizzard, “The next major patch will have some pretty fundamental changes to the game client. The number of back-end changes we’re putting in is substantial enough that we can’t just patch over the current content efficiently. As a result, when the next patch comes out, the client will fully reinstall itself to handle these changes.”
Blizzard claims that this is due to the fact that the upcoming patch will be a “remaster” patch which will introduce various fundamental changes to the game which explains why it is so big. They also note that due to the size that it can be a bit of an inconvenience to gamers who might not necessarily have the best connections, but they hope that by making this announcement that gamers will have time to prepare themselves for it. There is no fixed release date for the upcoming patch so we guess we’ll just have to wait and see.