In the article, Cameron Talks About The Future of New CGI Technology, he stated that with his new technology used on Avatar, an older actor could portray a young CGI version of themselves.
The president of Marvel Studios, Kevin Feige, stated that they would like to cast a well known actor to portray Steve Rogers aka Captain America. Though the chracter is in his late teens, and there arn't many actors around that either looks young enough, or actually is young enough to be considered a known actor, compared to Robert Downey Jr at least. I think you know what I'm getting at.
Would you guys accept James Cameron's technology used on an older known actor in The First Avenger: Captain America. And no it won't be like Terminator Salvation with Arnold. That tech isn't as perfect as James's tech. ????