I miss Arnold in movies like this but I really thought that T3 sucked anyway, I think it could possibly still work without Arnold but they have to have him in it somehow? The movie has time travel in it so you can go back to the T-800 days fighting "skeletons" no problem, they could have some "arnold" look-alike or cgi "arnold" t-800's that might be kind of cool? All they need to do is PLEASE make it better than t3!!!! They could also try a Back to the Future angle where they can go back in time with footage of the older movies being "re-created" with lookalikes or cgi or somehing? ANother possiblity have arnolds voice be in a computer or a t-800 skeleton? The time travel aspect means that they can change anything they want basically and just say it takes place in another time period,