Are Sword Art Online and Accel World related? Recently, I have been hearing loads of theories about Sword Art Online and Accel World being related due to the fact that they refer to NerveGear and such in Accel World. 

I have also been hearing that the plot of Accel World was made by Kirito.

Is there some sort of confirmation of this? Or trustworthy speculation?
The author, Kawahara Reki, didn't clearly say whether they are in the same timeline or not. During the Sakuracon Festival Interviews, he answered like this:


  When you were creating the Alicization arc in Sword Art Online, was the technology used in the Alicization arc carried over as a foundation to Accel World?
  
  It is true that the technology used in Alicization could be, or is the foundation of the technology being used in Accel World, but at this point, like I said, it might be similar technologies having a similar technological chain, but it hasn't been made clear that it is in fact the same world. The two worlds could just have a similar technological advance. Also, as I noted before, if I were to clearly state the two worlds are the same, the number of things that need to be resolved in order for such a thing to be clearly possible is, the numbers are tens of thousands of times greater than I can even hope to do right now! Seeing a movie like The Avengers, where it took a bunch of properties into one cohesive title, I have to say that the creative staff on that movie is quite amazing.


Original link is "Interview with Kawahara Reki" on Sutoraiku Anime.