Ok, let's speculate: Since it's the year of Luigi, what if the next 3D console Mario game is in fact... Super Luigi Galaxy? Releasing Super Luigi U and Luigis Mansion 2 is maybe not enough to make it a "Year" of Luigi.
I think YoL will basically end after the retail release of NSLU. I mean, they've got Wind Waker, Sonic, Mario Kart, Super Mario and who knows what else in the back half of the year. They aren't going to divert resources from those games to promote Luigi.
Year of Luigi was basically an easy marketing ploy to make it look like something was going on in the barren 1st half of 2013.
It was pretty awesome though