Optimus Maximus appeared a while ago in a smaller glimpse and has now appeared in full all over the net. He is said to be part of Wave 4 that is already on preorder for most of the online retailers.

Last night Big Bad Toy Store and TF Source have released pre-orders for the next combiner set. This series seems to be predicted months ago that it would include:

Deluxe Ironhide
Deluxe Mirage
Deluxe Sunstreaker
Deluxe Prowl
Voyager Optimus Maximus
Leader Class Starscream

(Big Bad Toy Store)
Deluxe: Ironhide, Mirage, Sunstreaker, Prowl
Leader Class Starscream
Voyager Optimus Maximus

(TF Source)

Deluxe: Ironhide, Mirage, Sunstreaker, Prowl
Leader Class Starscream
Voyager Optimus Maximus