Accordingly to Lorelle, WordPress 2.5 will be released before WordCamp Dallas.
As taken from WordCamp Dallas website:
The Dallas 2008 WordCamp spans two days, with the first day focusing primarily on general user topics and the second day primarily on developer topics, with some overlap.
In this case, WordPress 2.5 should be out on either 28th March 2008 or 29th March 2008.