The longer they leave it the less impressive it is going to look - I remember being in awe at the tech demos for HL2 and the leaked doom3 demo.
... but looking at them now and comparing to the likes of Far Cry with its stunning landscapes, water and lighting effects and Painkiller with its exceptionally detailed textures and high polygon counts they are going to have to release their games soon.
I'm still in no doubt that Doom3 will be absolutely stunning as Carmack is the master of graphics engines and always leads the way.
But goddamit I wish they would hurry up !!!