We?re at 3.4GHz already?surely 4GHz can?t be far away? Alas, even 4GHz seems to be remote indeed. In mid-2004, as you probably know, Intel first delayed its planned introduction of a 4GHz chip until 2005, and then in fall 2004 it officially abandoned its 4GHz plans entirely.
From the looks of it, we aren't going to be seeing those 'gigaherz' increase in our computer power any more....