Actually wave 4 is:
Brainiac (I always thought it was Metallo too but it seems this is how Brainiac is in the comics)
Superman (2-pack repaint)
Supergirl and Superman (wave 2 repaint) with black symbols aren't shipping yet but will be cycled into shipments through the end of this year. Also, wave 4 is the last wave for this year except for a 12" Batman and a 12" Superman that are supposed to come out next month.
Scroll down to the post by Boy Wonder, it seems he's doing a DCSH public relations thing like Jesse Falcon does with Fwoosh.
So we've got the rest of the year to look for wave 4, that's a relief since 3 and 4 came out so close together.