"simultaneously" for current and next-gen.
Lead software engineer Piotr Mintus boasts that Monolith was "one of the first studios in the world" to be running a title "on the PlayStation 4 alpha kits," with an engine updated with tessellation.
It would seem then that Monolith will be using their LithTech Engine, which they used in F.E.A.R. 2 and No One Lives Forever 2, albeit with rather obvious enhancements.
Guardians of Middle-earth has been Monolith's latest release, which launched in December, and recently got.