For me the iconic gnome will always be "David the Gnome" - something the PHB version has never even attempted to re-create. Its version, to me, has always seemed more along the lines of a magical halfling instead. So, if the Gnome is to be as it has been in 3e, then I wouldn't mind dropping it until the PHB2 comes out in '09.
Now, if they re-create the gnome to be a tiny sized humanoid or fey with a wisdom bonus, greater than normal speed for their size, and the ability to communicate with animals (even if only via Wild Empathy or something similar to that, as a racial ability), then I might be willing to accept them in the PHB. But I do not see that happening, as apparently they have been half sized magical humans for at least two editions so far, and as such tradition will likely dictate that they remain such for the time being. So, no, I do not wish to see them in the 4e PHB 1. In PHB 2, however, I could likely accept them.
I also wouldn't mind if the Tiefling (and its good counterpart) were similarly withheld until the PHB2 comes out, but it seems oddly more likely that a partial fiend (rather than a magical halfling) will be a common race in the default 4e presumed setting. All I can say is that if I decide to DM 4e, tieflings will likely not be allowed as a player race unless there is a major story / quest important reason for it.