If you were planning on purchasing any Transformers video games on Steam or the PlayStation Network over the holidays, it's too late. Activision's pulled them all, along with 2014's The Legend of Korra.
The disappearance of War for Cybertron, Fall of Cybertron, Rise of the Dark Spark and 2015's excellent Transformers: Devastation was first noted on Twitter by @Lashman (via Resetera), an excellent fellow to follow if you like to keep track of the comings and goings on Steam.
A quick search of the PlayStation Store showed that the same games were no longer available via Sony's storefront either, just a couple of listings for disc-only Transformers titles. All of the games are still available on the Xbox Marketplace (and very cheap), but it's likely just a matter of time before those disappear as well.
Activision has not responded to our request for comment on the games being pulled. It's highly likely their removal was related to licensing, as was the case with the great year-end Marvel game culling of 2014.
There's always a chance the games will come back one day in some form. Maybe a crappy remaster, like Marvel Ultimate Alliance. And if they don't, at least no one will ever have to feel bad about purchasing Transformers: Rise of the Dark Spark ever again.