Arnie speaks on TERMINATOR SALVATION and THE EXPENDABLES cameo
Regarding Arnie's cameo in TERMINATOR SALVATION, what I and indeed the Governator himself suggest is for fans NOT to expect him to turn up in the May blockbuster. That way, if he does appear in it, it will be a nice and genuine surprise for everyone. And if he doesn't, well then you weren't expecting it anyway. 
Arnie spoke to fansite The Arnold Fans...
I have seen the movie, but I have not seen it as a finished product yet. I have not seen it yet with the Terminator special effects and some of the sound and the music is not in there yet and so on. So I really cannot comment on it, what the movie will be like as a finished product. Theres a rule that you never talk about a movie unless you have seen the finished product. But you know as I said to the director when they began that I wish them the best of luck, that Im happy that they move forward with the franchise, I am very happy with where I am with my profession as the governor and they should try to find a way of doing a story that does not include me at all, not even one single shot in it. I dont believe in that. To kind of have them go out and promote the movie and say you know Arnold is in the movie and everyone thinks that Im the Terminator and in fact you only see one second of me in there and so I dont think thats the right thing to do. And you know thats the danger of that, and thats why I feel reluctant to be part of the movie in the first place. So it doesnt get promoted that way.And on his brief role in THE EXPENDABLES?
"So I... naturally when he asked me if I would do a cameo, which will just be something quick, like I walk out of a hotel or out of a office building and he will walk up and we will bump into each other and there will be some mumbling and then we will walk off (crowd laughs). So it will be something very simple, that will be again, just a cameo, so that's what we're going to do. I promised him I'd do that and I'm looking forward to that. Ok? Good".via - coming soon