A continual complaint for some that own both a Wii U and 3DS is the absence of cross-buy promotions, particularly with Virtual Console games but also with some download titles available on both systems. We have seen recent examples from Nintendo with Pushmo World discounts, and there's been a genuine cross-buy offer on Squids Odyssey in Europe, though it's limited to the region and you can only get the Wii U version free after a 3DS purchase, and not the other way around.
They're tentative steps, however, and Image & Form has indicated that when SteamWorld Dig arrives on Wii U, those with the 3DS version may be able to enjoy a discount.
This kind of promotion certainly makes sense when releasing any port, in a sense, to motivate gamers into double-dipping. Are you planning to pick up SteamWorld Dig on Wii U or, if you're on the fence, would a promotion to own both be tempting to you?
Thanks to Ryan Millar for the tip.