Audi definitely only supporting customers in 2004 as per press release recieved this morning:
In addition to the works entry in the DTM, the Audi marque will continue to be actively involved in sportscar racing with the successful Audi R8. During the 2004 season, Audi Sport will support customer and importer teams at the 24 Hours of Le Mans, in the American Le Mans Series (ALMS) and in the new Le Mans Endurance Series (LMES). Audi will make their works drivers available to the teams Champion Racing (USA), Goh (Japan) and Veloqx (UK), first and foremost Le Mans winner Rinaldo Capello and the defending ALMS Champion Marco Werner. A new member of the Audi sports car squad is young German Pierre Kaffer (27).
All sorts of rumours flying around about their proposed 2005 involvement.
Manufacturer support thin on the ground in the LMP categories for 2004 unfortunately.