Without getting too deep into this, I think Parcells actually has someone in mind. It's no accident that Henson never saw any preseason action. In the scrimmage, his only action, Henson looked the best of the three QB's. Had Parcells played Henson in the preseason, and had he lit it up, then it would have been much harder to cut him, which it appears is what Parcells wanted to do from the start. He wouldn't have been so set on cutting Henson, unless he had someone else in mind to cover his bases in case Romo just cannot handle it. An experienced mid-line back-up who has some NFL experience, who Parcells knows pretty well.
One name comes to mind, and he may be released in the next week or two. Tim Hasselbeck. Parcells former ball boy with the Giants.