Recently, Borderlands Producer Stephen Palmer stated, "I think we can do even better on the single-player front by doing a bit better on the storytelling aspect and focusing a little more [on] iterating on our AI systems, and I think by doing those two things we can bring even the single-player experience up to the level of the co-op play."
He went on to say that the storyline was placed on the back-burner as they concentrated more on the core of the game; guns, explosions, guns, enemies exploding, guns, and big-ass enemies dying from even bigger-ass explosions resulting from guns that fire exploding rounds while playing with your friends. I may be paraphrasing that last bit, but it doesn't mean I'm wrong.
The team's hopes are to bring a sequel with a more compelling storyline while remaining true to what brought the series the adoration it rightfully deserves. The hope to so fill out the single player experience so that the co-op portion of the game doesn't take center stage. From the point of view of someone who loves RPG games for the storyline, this is amazing news.
Borderlands director Matthew Armstrong also pointed out that a second playthrough was almost left out of the game. A majority of the creative team didn't feel it was necessary, but Armstrong pushed for it and we all benefited. In fact, the reaction to the second playthrough was so overwhelmingly positive that for the sequel they also plan on including more endgame content for those of you who max out your characters and need more of an challenge.
From what it sounds like, the team at Gearbox aren't just sitting back and smoking congratulatory cigars. Regardless of how well received the game was, they are planning on making it bigger, better, and more explosive than before. Let's just hope they don't get caught up too much on the next big technology or we might end up with another Duke Nukem Forever.