Short version: Yes, Adaptive Style lets you recover all your expended maneuvers as well as choosing new readied maneuvers.
Admittedly, the text is not abundantly clear. My reasons for this reading are the following:
It can be derived from the rules.
Adaptive Style references the rules for readying maneuvers (they must, how else would we know what the concept even means?). The rules for readying maneuvers do not contain any information about "partial readying", the rules describe a mechanism for readying all of them for use.
The FAQ agrees.
Page 38 of the 3.5 FAQ states much the same:
Q: If a character uses the Adaptive Style feat (ToB 28) after he has expended some of his readied maneuvers, does he choose new readied maneuvers equal to the maximum number he can ready, or equal to the number he hasn't yet expended?
A: Using the Adaptive Style feat completely resets the character’s readied maneuvers, making them all available for use. If you're a crusader, you also reset your granted maneuvers.
Alternative readings result in undefined behavior.
Is it possible to ready a maneuver in an expended state? What happens if you switch out an expended maneuver for an un-expended maneuver?
It is balanced and results in superior playability, particularly for the Swordsage.
It is known that the Swordsage's recovery mechanic is too poor for effective in-combat use. Even with this reading of Adaptive Style, in-combat recovery is very difficult for them. Without it, a Swordsage very easily turns useless after the initial rounds.
And all the martial adepts can run into the problem of having the wrong set of maneuevers readied. This reading of the feat makes it possible to recover from such bad decisions (at the high cost of a full-round action). It's more fun all around.