I found
this using google on "Crossbow" AND "AKU 2.0".
Seems like Crossbow, which is supposedly a second edition of WM5.0 like WM2003SE was to WM2003 is slated for a Q4'06 release with a Q1/Q2 '07 marketing launch. I have read in other reports that it was suppose to be released in 1H'06. As I don't see any dates on the link, I don't know if the release date has been pushed back.
Photon, which is suppose to be the next big mobile OS upgrade, it seems will not be until late 2007 and marketed in Q1/Q2'08.
“Photon” (Q4 ‘07)
New, Flexible Shell
Modular Containers
“Yamazaki” CE kernel
Q1/Q2 ’08 Marketing Launch
“Crossbow” (Q4 ‘06)
Great mobile messaging
Advanced Business and Enterprise propositions
Strengthened phone experience
Faster, easier application development and distribution
Q1/Q2 ‘07 Marketing Launch