I had the same question and asked NIK software support. Their reply was they are seeing no problems with Aperture 3.4. I subsequently upgraded to 3.4 without any problems and verified the NIK plug-ins work as they did before.
Note that NIK updated all their plugins on 13 Sept. I do not know whether you need the updates to avoid problems. I updated my plug-ins prior to upgrading to 3.4.