They didn't know it wasn't coming though. If you read the SMS forum you'd know this. When they got to the point where they weren't getting any more performance out of the system, they flat out told the public about it. They spent time and resources on optimising the code for the Wii U, and got a maximum of 23fps @720p. AFAIK Nintendo demands a minimum of 30fps and 720p, so there wasn't much more they could do at that point. Ian said in the forum that they were waiting to find out about Nintendo's future plans regarding hardware, and if no new Nintendo hardware would be coming any time soon, they would look into other options, like cutting the game down. If it's been officially cancelled, it would be due to them not wanting to release such an inferior product, as to get the game to work, they'd need to run practically completely different physics, and reduced, or no weather.