Demi Lovato has recently did a question and interview through her twitter video when a fan asked whether if she would love to do a duet with Christina, she replied as below:
Christina is one of my biggest inspirations, and I would love to do a song with her. That would be a dream come true. We have to make this happen.
You guys can take a look at the video here: https://twitter.com/ddlovato/status/663686931826532352
I will definitely looking forward to see a super duet from both of my favorite artists!