It could potentially be a system seller, but only if they drop the New Super Mario Bros branding. That series has been stale ever since 2012, so releasing another one would do absolutely nothing. If they come up with a true 2D Mario successor that actually shakes things up, I could see it becoming a hit.
Also, not buying the idea that Mario Maker is a true replacement. There are a ton of people who would rather play an entire game of professionally made levels than the noobish quality that fills Mario Maker.







