That is just what is currently working on DOOM3, however it has been clearly stated in the past, and again to me while at QuakeCon by a couple of employees that there are vague plans for a multiplayer follow-up patch or product for DOOM3 that have not been fully decided on. So dont panic! all this means for multiplayer is that the singleplayer version of DOOM3 may be including a limited multiplayer portion although probably not. Just keep your pants on and wait for the multiplayer patch/expansion.Bron : Gamers.nl
Multiplayer in Doom3

Na dat er gisteren bekend was gemaakt dat Doom III maar maximum 4 personen multiplayer zal laten spelen is ShackNews een beetje op onderzoek gegaan en er zouden plannen bestaan voor een multiplayer patch , of zelf een hele multiplayer uitbreiding