It's probably too soon to know what this means, but a pair of European store websites have posted listings for an "enhanced edition" of The Witcher 3, with a February release date.
French retailer e-Leclerc and Belgian store Smartoys have both posted the listing (via NeoGAF, as usual), and neither says anything about what would be enhanced in this version of the game, nor any other real info at all beyond a February 5 release date.
Both previous Witcher titles received enhanced editions that made significant changes to how they played, and added new content -- and they were free to existing owners and thus functioned as particularly beefy patches. The Witcher 3 was obviously a completely different sort of production from the previous two games, however, so whether it has any need of an update worthy of being called "enhanced edition" is certainly up for debate.
That said, the second paid DLC, Blood and Wine, remains unreleased and without a scheduled date. A Witcher 3 Enhanced Edition could be an all-inclusive package released alongside Blood and Wine akin to new copies of Destiny purchased since its Taken King expansion hit last year, or a standard "game of the year" edition bundle.
Hard to say how reliable any of this is. Video games, I love em.