Dr. Serkan Toto, Industry Analyst, posted on Twitter earlier today, confirming that according to his sources, Super Mario Run was still on track to be released this December.
Surprisingly though, the title is not being developed by Nintendo itself, but by mobile partner DeNA.
https://mobile.twitter.com/serkantoto/status/788418082846887936
Dr. Toto did mention in a separate tweet, that Shigeru Miyamoto is overseeing development.
Super Mario Run will be Nintendo’s first Super Mario game for mobile and will be exclusive to iOS.