Arnold Schwarzenegger has addressed the possibility of appearing in an Avatar movie, but only if a particular condition is met first. Schwarzenegger and Avatar director James Cameron have worked together three times, and have become friends in the process. As a result, it may not be surprising that the two have discussed the upcoming Avatar sequels. Cameron directed the first two Terminator movies as well as True Lies, all of which starred Schwarzenegger. All three of their past collaborations were successful, but it has been over 30 years since the two worked together.

https://screenrant.com/arnold-schwarzenegger-avatar-movies-character-james-cameron-cast/