Prime Season 2 details (from NYCC) + teaser clip
IGN website posted up details from the Prime panel at NYCC, plus, Tformers posted up the teaser clip from Season 2 (recorded with someone's phone).
Be aware that since these are Season 2 details, if you haven't seen all of Season 1, there will be spoilers.
Details from the panel included:
Bumblebee's voice (or lack of) will be explored in a 2-part story early in the season.
Maybe some upgrades to characters by the end of the season.
Wheeljack and Starscream will return.
Some new characters may not turn into vehicles.
The story will leave Earth for a while during Season 2.
They want to do Dinobots (but sounds like they aren't in this season though).
A character called Dreadwing will appear.
And there will be a higher body count this season, which can include "anybody".
The panel ended with the clip linked above, which is about 10 seconds of Knock Out applying a Decepticon symbol on the arm of Orion/Optimus.