Im sure Vin Diseal would get touted around but I think he would be wrong; purely because he has no sense of humour or at least comes across that way in his movies and in person.
To play Duke, you need someone who wont take things seriously and would just have fun playing the role. Arnie acting serioulsy would have been perfect, since Arnie "acting serious" is basically Duke Nukem! lol
Anothe rgood choice would be Aaron Eckhart.
However, we all know that if a movie is made it will most likely be directed by one of the crap trinity (Anderson, Bol or McG) and it will turn out to be a piece of crap.