I would love to see an armored hero character like Eomer or Theoden come next. I hope that the long delay between announcements is due to the complexity of the armor in the next piece. But at this point, the less complex fourth piece in line may pass up the third and get announced first, as I suspect happened with Luke & Yoda beating Boba Fett in the Star Wars line.
Also, Boromir is very high on my list of most wanted LOTR PFs. His costume would look fantastic, and he would be a logical companion to the existing Lurtz.
I have seen plenty of Gandalfs and Aragorns and Legolases (Legoli?) so they don't interest me as much, but I suspect that they are high on the list of most people so we will probably see them sooner rather than later. But I am much more interested in characters that have been under-represented so far--I would take a Faramir or Fountain Guard or Easterling PF over some of the more oversaturated characters any day. (Although I eventually want the entire Fellowship in PF form.)
But of course, I would take ANYBODY right now. If any other line went over a year with no activity, we would just assume it's dead and move on. But the potential for LOTR PFs is so vast that we keep holding out hope for another announcement. I really did think we would get news at Toy Fair, but the wait continues...
