It seems that the chain of sources on this leads back to a bogus story.
The story apparently originated at an Arnold Schwarzenegger fan site and with the lightning speed at which news stories make the rounds online it was picked up very quickly and appeared on a number of movie news sites (including this one). Seems it was made up by an overeager contributor to the site.
Now although the story has proven to be a complete fabrication, I still think the idea is a good one: Schwarzenegger, whether in person or via CGI should appear in these movies due to his association with the role.
For the full debunking story you can go here.