They're probably stuck in something. It's happened to me, I had to quit game (on 360) and start it up again. Apparently invisible creatures infest Skyrim and grab your intrepid journeymen by the ankles, rooting them in place.
Not sure this is the same issue some of us are having.
I have waited in game for days, just waiting. Its also been almost two in game months since I "lost" my follower.
Thing is, I dismissed my follower a long time ago and have been unable to hire a new one because "I already have someone".
Using the console commands I found out that "playerfollowercount = 1.00" but I am unable to figure out who is supposed to be my follower.
Not only is this annoying me, as my wife can not travel with me, its also blocking me from any quests that requires anyone to follow or join me for any reason.
I really wish someone would come up with a solution, if there was a way to target or find the id of the NPC who is supposed to be your follower I could try to disable or kill them and see if that fixes the issue.
However I am still new to using the console and this would not help out anyone on the PS3 or the 360.
I already contacted a mod, but I am not sure they can do anything.
If I knew how to contact the devs directly I would.
I know at times the devs have posted here on this forum, it would be great if they would at least post that they are aware of this issue (and others) and are working on a solution to fix it.
Having my in game wife follow me was something I was looking froward to, but now I have a ghost follower and have been unable to hire another.