Villa are our main rivals at the minute because we are in the same league...same as we are with them. However, once we are back in the same league as Wolves, for me they will always be our main rival, and Blues will always be Villa's main rival.
Suppose it depends on where you were brought up etc...living in Wall Heath/Kingswinford, its very much Albion and moreso Wolves territory.
I have to say though, I think it could be a while before we play the Wolves in the league again...same goes with Blues, and if when Villa go down, there current squad doesn't strike you as one that will definitely bring them back up! It could be a while before we have a decent derby again (providing we don't collapse!)