Its called IBM System i nowadays, and hasn't been called AS/400 since 2000 [1].
FTA: "We will provide further communication on supported generations prior to POWER7+, including firmware patches and availability."
POWER7+ is used in since 2012. They all seem to be based on POWER architecture these days (first devices using PowerPC/POWER3 in 1997).
Also of note, the firmware patches will be available on jan 9 but they also require OS patches. The Linux patches will be available on jan 9 and the AIX patches arrive on feb 12. They don't mention IBM i (OS/400) at all.