As is usually the case when a new character drops, the update will primarily add support for the new fighter, stage, and Mii Outfits that will become available to download. It'll also include fighter adjustments, so make sure to convert any replays you want to save before they're no longer available.
We'll make sure to update you with the full patch notes as and when they arrive. Min Min will become available on 29th / 30th June depending on your time zone, so we'd expect the update to appear then.
Until then, feel free to check up on past patch notes here:
Looking forward to the new update? Will you be buying Min Min or the second Fighters Pass? Let us know with a comment below.