Not a port or DLC, apparently
Paradox Interactive is no stranger to making announcements at the Game Developers Conference, and it seems GDC 2013 will serve as a launchpad for something new related to Magicka. PC Gamer was told that such a reveal will happen during the March 25-29 event and it's not going to be a port or more downloadable content.
An honest-to-goodness sequel would be -- now that the original game has built up an expectation-breaking audience -- much appreciated, I'm sure. Magicka: Wizards of the Square Tablet isn't really my thing, but a true follow-up likely would be.