Blizzard announces the ladder reset and installing the patch 1.13 for Tuesday, March 23, 2010. Although we do not yet know the exact times, kingdoms should be unavailable for a period of approximately 6 hours (see message - thank you and Florent Hillda).
As usual during a reset, all ladder characters (tournament) will be transferred to non-ladder fashion. Your characters and objects will not change course, but you will by more cons object access reserved for ladder mode, like some runewords. For more info about the different types of characters introduced since version 1.10 of the game, I invite you to read this page.
Regarding the patch 1.13, I remind you that the entire patch notes in French and is available at this address. This is not final but should be very similar to what we see land on the Live realms March 23. The time has finally come!