I will look into the details, but as far as I know, the contract is binding for three years. Meaning, he cannot move to another city unless his current employers trade him to that city for whatever price.
So if the Kings XI says to Delhi, keep your $2 million, we'll just keep paying Marsh what we do now, then Marsh is out of luck. If, on the other hand, Kings do take the money and send him to Delhi, for example, then I think Marsh can renegotiate.
But I can't provide proof that this is true, I'll try to find the contract online. I know Goughy or I found it before, so a link is somewhere on this site.