Existing services run by Bungie to cease, with replacement functionality provided via Halo Waypoint.
On March 31 the transition process for Halo data from Bungie to Microsoft's 343 Industries will be complete, with all Halo data managed by the Halo studio.
From this date Bungie will no longer be able to update game stats and player service records, to host new user generated content, or to operate the Bungie Pro service. Bungie notes that "all currently supported, Bungie-developed Halo titles will be impacted by this change".
A blog post adds: "Any replacement functionality, and all future Halo support, will be provided by Microsoft and 343 Industries via Halo Waypoint at http://halo.xbox.com.
"Bungie will preserve all existing historical Halo data on Bungie.net for as long as the Internet and Bungie's data storage systems remain functional."
Halo 4 is scheduled for release this winter.