When Yacht Club Games unveiled Shovel Knight's multiplayer expansion, Showdown, last August they hoped to have both that and King of Cards ready by April 9. That's unfortunately not going to happen anymore.
The studio has announced that both physical and digital editions of Showdown and King of Cards and the Treasure Trove amiibo 3-pack have been delayed "several months - at most". They've chosen this vague phrasing because they don't want to have another delay, so we won't get specifics until they're absolutely sure things will be ready by on the announced date. Hopefully, this means we'll get these final expansions before fall sets in.