The Yacht Club Games website has details on a couple of new campaigns that are coming for free to Shovel Knight along with all the other post-release content for the platformer (thanks Eurogamer). Here is the summary of their battle plan:

With that experience fresh in our minds, the team here is now working on all remaining campaigns and updates at once! That means Specter Knight, King Knight, Body Swap, and Battle Mode (for PC and consoles). That’s a lot more game — and it should arrive sooner than the wait between Shovel Knight and Plague Knight. Creating these updates simultaneously will allow us to plan more cohesively. How levels change between the two characters, how much time is needed for new mechanics/systems, stories interweaving, and so on. Once we’re nearing completion on one set of updates, we’ll be switching our focus to a single campaign to make sure it’s polished for release. Then we’ll be doing the same by switching to the next campaign! Here are some answers to the most frequent questions:

• We’re working on two new campaigns: Specter Knight and King Knight.
• Campaigns will not be releasing at the same time. Specter Knight will be released first!
• No estimated release date for any Update quite yet.
• Similar to our last update, we’ll probably go overboard too. Hey! Maybe that’s why we’re called Yacht Club Games!
• New campaigns will come with new Feats and Challenges for the new campaign character!
• We’re also working on two new modes: Body Swap and Battle Mode!
• Just like Plague of Shadows releasing with Challenge Mode, we’re planning to release one of these new modes alongside each campaign.
• Battle Mode is being designed as a single screen, multiple controller, multiplayer mode and is currently not planned to arrive on handheld versions of the game. We’ll be sure to announce if there are any changes on that front.
• Much like Plague of Shadows, all of the announced upcoming Shovel Knight content will be free on ALL platforms! For disc/cart and digital versions!