If Bell wasn't injured, Morgan wouldn't have been picked
In my view any suggestion of dropping either Cook or Pietersen is barking, unless we have people ready made who could open and average 45 and bat at 4 and average 49 over 50 tests as these guys do.
In any team there are batsman who are in form and out of form, but you also need to maintain consistency to ensure the best performance from a batsman.
Given how the team are playing, I can't see that there will be any changes to the team ahead of the ashes, so when Bell gets fit he will almost cetainly miss out - unless one of the batters gets no runs in this series.
I actually think that Trott shouldn't be pushed up to open, but if Cook is to be dropped, Bell should open in his place. That way the batting order stays as settled as possible, which is really important.
Personally I think that we have too many natural number 5's in our team, with Bell, Collingwood, Pieterson, Bopara and Trott all more naturally suited to the number 5 at test level.
There is zero chance of KP being dropped.