Battlefield 2 Revealed on Computer Gaming World (thanks Frans) teases the full announcement of the next installment in the Battlefield series in their July 2004 print issue:

That's a tentative title, of course. The game isn't a direct follow-up to Battlefield 1942 or Battlefield: Vietnam. Instead, it jumps forward to the world of modern warfare. The sequel will feature the latest in modern small arms, heavy weapons, and fighting vehicles -- M-4 carbines with IR scopes; M-60 machineguns with steadying bipods; M-1 tanks with reactive countermeasures; and of course, much more.