I have never agreed with the idea that preparing pitches to suit the home team is somehow illegitmate. IMO it's part of test cricket and one of the things that makes an away test series win special. After all whatever the nature of the pitch, it's still the same for both sides. If they prepared a turner for the Oval, and England managed to win that would simply reflect their better spinners which is a legitmate area of superiority.
Of course regardless of what the Oval curators end up preparing you would hardly expect them to announce it in advance. So it's quite possible that they will prepare a turner anyway. If however they do prepare a fairly flat track I think it will be goodbye to England's chances. They probably don't have the attack to win on a batting pitch especially given Flintoff's dodgy status.