Just out: LOCKE & KEY: MASTER EDITION, Vol. 1.
This book collects the first two story arcs ("Welcome to Lovecraft" and "Headgames"), and features a handsome new design and sexypants new cover art from Gabriel Rodriguez.
I doubt we'll ever do an Omnibus edition. I'm not a fan of the format. They're so heavy and cumbersome, it's impossible to sit and read them comfortably without spraining a wrist. The Master Editions, which will serve up all 6 arcs in 3 books, strike me as a more appealing alternative: the books are beautiful and you've got the whole story in just a few volumes. If you've never read Locke & Key, the Master Editions might be the best way to jump in.