I whole heartedly believe that 2D Mario will continue to exist. I just have no idea if proper Nintendo built 2D Marios will continue to exist alongside Mario Maker. I believe they can and should coexist, as I think both will sell well, but it'll be interesting to see if Nintendo sees the need for proper 2D Marios when they can just rerelease Mario Maker, add slopes and some new level themes and call it a sequel, then watch as everyone throws money at it.
What I think would be a pretty amazing, albeit extremely unlikely compromise, would be doing both at once in one game. Release the next 2D Mario with both a proper campaign and the extensive level creating suite from Maker. Nobody would lose out of that. Nintendo wins because it'd probably quite easily be the most acclaimed 2D Mario since World with the sheer amount of content and would likely sell accordingly. Fans win because they get the best of both worlds. Then again if they did that, they lose the opportunity to make significantly more money by releasing them separately...







