First up: Shovel Knight is getting renamed to Shovel Knight: Treasure Trove. The swap in nomenclature represents everything that's changed about the game since its launch, like adding new campaigns, two player co-op (coming to all consoles aside from 3DS and Vita) and a few other new features. Beyond that, when Treasure Trove launches, you'll be able to start each campaign independent from finishing the main game. Previously, you had to beat the first game to unlock access to the expansions.
What's more, the base game has been renamed to Shovel Knight: Shovel of Hope to bring a bit of uniformity to how all the campaigns are named. Beyond that is the news that this year will see a story featuring King Knight and Battle Mode. Yacht Club promises that the update process will be a smooth one for existing owners and that all the new stuff will be added free of charge via software updates.
And speaking of cost, this spring Shovel Knight will go up in price. Yacht Club didn't elaborate how much, however, but teased that picking up individual expansion packs might be cheaper than buying the game outright. Hrm. For any other questions, the studio says to ask away and it'll try answering them on this FAQ page.