“Microsoft Corp. will share more details on the next version of Windows, code-named Longhorn, at its Professional Developers Conference (PDC) next month. However, the company likely will keep the new user interface, dubbed Aero, under wraps.

Aero may make a cameo appearance in Microsoft Chairman and Chief Software Architect Bill Gates‘ opening keynote, but is not finished yet and likely won’t be included in the pre-beta release of Longhorn that will be handed out to PDC attendees, according to sources familiar with Microsoft’s PDC plans. Also, Aero is not on the calendar of sessions at the show.

Perhaps more important to developers is that Microsoft will give PDC attendees the scoop on Avalon, the little talked about engine underlying the Longhorn user interface. Microsoft has described the technology as ‘a brand new client platform for building smart, connected, media rich applications in Longhorn.’ Developers at the show will be told how to take advantage of Avalon in their applications.”