It would be interesting to see the return on actors from the original films but the focus should be on a younger and more energic cast. Linda Hamilton's character Sarah Connor died before Terminator 3 so it is not logical for her to appear unless the story somehow requires her. But Arnold Schwarzenegger should definitely be back! I would love to see an Irish actor play a bad Terminator. I love the accent in Northern Ireland and have become a fan of aspiring actor Paul Curran. He was in Britain's Got More Talent earlier this year and acted out a famous scene from the Liam Neeson film Taken. The world is aware of the conflict in Ireland but there is also a lot of talent here, yet to be discovered in Hollywood.

yeah, I cannot agree more

While I wouldn't like to see Arnold as he was in previous films (a small side role and/or him being human would be the only way I could see it being a good thing).

Haven't heard of Paul Curran before so I can't comment. But Irish accents are awesome =D

Arnold as a human = Fail "Trust me".