GATE 7 Volume 1 will be on sale June 3rd for 460 yen.
CLAMP will also indirectly participate in a charity event April 23rd at Kawamata, a city whose local economy had plummeted because of the nuclear disaster. CLAMP has donated a CLAMP School Detectives colored illustration to the event. Details can be found here.
ETA: Mantan-web report with image