Are there any crossovers of SAO and Accel World? Anime, manga, light-novel, anything?

I saw this image a long time ago somewhere:

[![Black Swordsman, Silver Crow, and Cartman][1]][1]

And I read about a possible crossover between the two. Does anyone know if it has aired yet or will be? And where I can find the episodes/chapters or find more information?

  [1]: https://i.sstatic.net/fyGMb.png