Well, this is all out of nowhere. According to Venturbeat:
"No immediate replacement has been appointed, but Autodesk says it has “formed an Interim Office of the Chief Executive,” which will lead operations until a replacement is found. This will be led by Amar Hanspal, senior vice president and chief product officer, and Andrew Anagnost, senior vice president and chief marketing officer. Hanspal and Anagnost will be interim co-CEOs."
“I am not leaving to spend more time with my family — that presumes my family wants to spend more time with me,” he noted, somewhat humorously, in a separate open letter. “I will, however, be spending more time in my shop with my robots. I also have some other plans and will have more to say on what I’m doing in the next few months.”