I probably wouldn't worry much about preparing pets for WotLK because when it comes out it will have new cool pets with new abilities. Until you have the chance to try those out in a multi-boxing scenario you won't be able to make a fair decision of what will work or not.

We all can look at what is being released daily from the beta account and have lengthy discussion about how different classes will work and what not. Fact is it is in BETA, things are still changing, in fact the hunter talent "Hunting party" just got nerfed ... DK got a whole wackload of talent changes and so on. Enjoy what you can play with now ;-)