Best not to give it to your best bowler/batsman. Think someone like Collingwood, Cook or Strauss should be considered instead of Pietersen whose own form has been patchy in recent times.
The problem is that ideally you want a captain who is guarenteed to play every game at both Test and ODI level. When you look at the England setup there's only so many players who fall into that category.
Collingwood, dunno, need to see if his ton was a revival or just a positive blip.
Strauss didn't really convince me as captain a couple of years back.
Cook just doesn't strike me as captain material, not yet anyway, maybe a few years down the line.
There's not really any names glaring out at me right now, Flintoff has the heart but I'm not sure how well he'd hold up again under the burden of captaincy, he really needs to get back to 100% first.
One a related note, the fact Vaughn is taking a break opens up another spot at the top of the order. I guess the question is whether England bring in another specialist batsman or go for a more rounded approach by including all of Flintoff, Collingwood and Broad..... does look potentially a bit weak in the middleorder though and could prove tiring for those asked to come in shortly after bowling:
Cook
Strauss
Pietersen
Bell
Collingwood
Flintoff
Broad
Ambrose / A.N.Other
Sidebottom
Anderson
Panesaar