Is vBulletin going to have a mega mod hack like Infopop has. I think it would be a very popular feature.

As I remember, you can define a usergroup as board mod, in vBulletin 2, not sure in version 1.xx

If by "Mega Mod" you mean a person who has moderator permissions in all forums, it is already built-in. Set the person's usergroup to Super Moderator.

I have several Moderators for the various forums that I have, I also have 1 super Moderator, but I want to set up a Temp mod feature, so that all moderators have the ability, to log in as temp mod to access move/delete forums that they do not normally moderate, this is only used if urgent, or the normal mod for that forum is not online. But if I make this temp mod a supermod, then he will have access to a private forum that is also set up just for admins & supermods, I do not want anyone else having access to these forums, what can i do?

You should be able to turn off the permission to access that private forum for the super mod temp handle your creating.