This basically means the voice cast (with a few exceptions like Optimus, Megatron, Brawl, and Thundercracker to name a few) is a semi-.hack//G.U. reunion.
From the Italian dub: while Optimus Prime, Bumblebee and Ratchet have the same voices as their Animated selves, we have some Beast Wars guys between the voices: Megatron and Starscream are Terrorsaur and Quickstrike. Also, Jetfire and Soundwave are respectively Tristan and Pegasus, and Air Raid is Piccolo.
I Knew It: Transformers Prime is set in the same universe as "WfC'' and during Ratchet's recap of the events during "One Shall Rise, Part 3" confirms that the being listed only as "Core" in the credits was indeed Primus.