If you are concerned about transferring because of virtual realms, id wait. They still haven't released information on how exactly it will work. Things like which realms, and how many are still not released.
No idea (outside of Blizzard boardrooms) how servers will be grouped up, so it's probably better to wait and see. If you're on a totally dead realm and desperate to go elsewhere, go nuts, but I would wait it out if possible.
If you just want to have more people around you without haveing to transfer, wait for Virtual Realms, or atleast the Blog on how they will work. Since thier basicly merges.
If you have a destination in mind or want to be around certain specific peopel in a particual realm, you'l still need to transfer.