The only system I've ever sold was my Xbox 360 S and that was one and a half years after I got it. I felt like I wasn't into the ecosystem that much. I'm not going to sell any Nintendo console I own because I know I'll truly end up regretting the decision by the end. There's too many games I haven't completed on Wii U and even then I'd rather keep it anyways, so I'm not going to sell it.
I'd probably have sold my PSP (the only non-Nintendo console I own as of now) as well, but I don't really see the point in doing so nowadays.
I'm not really sure how, but maybe they could take some losses in a specific part of their product line and recoupt the costs of the service by releasing software? I do get that they prefer to sell hardware and software at a profit, so let's scrap that.
Rather, they could recoup the cost of the service on each system being sold, as was the case with previous systems. That way, they could keep it free (or at least, free in some fashion)... though that would end up raising the system's price a bit. I don't really know, to be honest.
I did say I'd try giving it a chance as long as it is cheap, so once the full pricing details about this service have been put out later in the year, I'll look into it.
I'm not sure how would that even work considering Wii U uses a dual-screen setup. The grand majority of Wii U games have the GamePad mirror what's happening on the TV screen, but there are scenarios where you truly need it. That would require re-programming the software (or overhauling it entirely in the case that the GamePad screen is rendering something different at all times) and by that point, you would just rather make it an enhanced port instead like Mario Kart 8 Deluxe. I know Mario Kart 8 doesn't use the GamePad much on Wii U, but still.