Fantastic news! I knew they were going to do something, but it's great to finally hear the scale of it. I'm certainly looking forward too it, I need me some more Trine 2.
I don't know if this applies to the console versions yet, but it is worth noting the PC version just got a shiny update today including several nice options. It adds Hardcore mode, which only allows characters to revive at new checkpoints, the option to turn off self-levitation(the double plank surfing), and the option to turn off co-op levitation. All very nice if you ask me. I may just have to try the DLC in Hardcore mode from the onset, just for the extra masochism of it all, heh.
Oh, also, they released a teaser
for the new DLC/Expansion. ^^