The only time the producers did a follow up of a series was with Macross 7 and even that was not considered a full fledged continuation but a set of random episodes. I'm not talking about movies here either.
At best we will get a movie or a couple of oav's. Still, as most of you know we were presented with a 'resolving of the triangle' predicament in an interview. The chances of a second series are rather slim if even they existed at all.
I don't mind closing a great series like Frontier. An end is an end and I would hate to have a cliffhanger after all of those episodes. What I would look out for is a movie like DYRL. Let's just hope that the ending will not make us stand in the check up lines at the airport while on our 'Rest of the world to kill the director campaign'.
