I'm rather puzzled about how the warblade's maneuver replacement works with higher level maneuver prereqs. Do maneuver prereqs need to be fulfilled after I've already taken that maneuver? I'd think yes, but I haven't seen anything explicitly stating it either way, unless there's a more generic rule somewhere that applies that I don't know about.
For example, lets say I have one White Raven level 1 maneuver, Leading the Attack, by character level 5, enabling me to take White Raven Tactics which requires one White Raven maneuver. At char level 6 I can replace a maneuver. Can Leading the Attack be replaced by ANY maneuver and potentially 'circumvent' White Raven Tactics' prereq? Or can it be replaced only by another White Raven maneuver so White Raven Tactics' prereq remains fulfilled? If yes, would that other White Raven maneuver have to have been obtainable before WR Tactics (not requiring one White Raven maneuver as a prereq?) Or can it not be replaced at all since it was used to fulfill WR Tactics' prereq? I feel like I'm missing something obvious if I can come up with that many possibilities..
Maneuver prerequisites refer only to learning the maneuver. Once the maneuver has been learned, it can be used regardless of whether the character still fulfills the prerequisites.
For comparison, see the language used for feat preprequisites:
and contrast with the "Prerequisite" section of page 44 of the Tome of Battle:
Switch out the maneuvers you have used as prereqs at will, there are no side effects.