I think there is a good chance Butcher will tour to Pakistan. Yes he is getting older now but I think he could add some steel and experience to the middle order especially with the likes of Hussain and Thorpe now gone.
I would still pick Bell because it would be unfair to drop him after one poor series, especially since we won it! If for example Vaughan, Strauss or Trescothick etc picked up an injury though you could end up with a middle order of Bell, Pietersen, Joyce?? This would be very inexperienced. I would go with Butcher as a backup batsmen because he's been there and done it. I think the younger players need to be brought in slowly and at the right time, not just threw in at the deep end.
For example if Simon Jones had been injured in the first test then I think Tremlett would have replace him in the second. Since it came down to the last test, the biggest game in English cricket for 18 years or so, it was not the time to give a debutant the chance.