The specter of death hangs over this one.
http://www.nintendoworldreport.com/news/43422/next-shovel-knight-expansion-receives-release-window
The next Shovel Knight expansion will drop in 2017.
Yacht Club Games tweeted the expansion's logo today showing the Specter Knight campaign will be next - "Shovel Knight: Specter of Torment" will launch next spring.
— Yacht Club Games (@YachtClubGames) September 12, 2016
This update will launch with one of the other Kickstarter stretch goal modes - either Battle or Body Swap mode. with the other to come with the King Knight campaign.