Rumour has it the 3DS title is making its way to the Wii U thanks to a comment by a retailer on their website. At this stage is unclear if this a slip of new information or an error. Chances are it is an error as retailers are famed for announcing games not in development. Newegg the website responsible, which is hardly what you’d call reputable, is the only website making this claim. Luigis Mansion wouldn’t be the first 3DS game that was falsely claimed as crossing over too Wii U either, Kid Icarus being another.
That said, as a fanboy, I would love a port, the idea gets a thumbs up from me! It would be even better if a brand new Luigis Mansion game was in the works for Wii U. Still, this rumour seems highly unlikely.