According to Gearbox VP Steve Gibson, advancements in technology have allowed Borderlands 2 to grow “about 50-60%” larger than the its predecessor. This information was revealed during an interview with Game Master where Gibson also went on the record stating that the size of some cities contained in the sequel would not have been possible in the first game.
I wouldn’t be surprised if it was about 50-60% bigger [than Borderlands 1], but it’s also so much denser. Heck, just the city of Sanctuary, something like that couldn’t exist in the first game. Our technology has evolved a lot to enable us to do that now
Furthermore, the interview revealed that the team decided on making sure that those who missed out on Borderlands 1 won’t feel lost at any point during the sequel’s story.
A decision that was made at the very beginning of the game was that at no point at any time could someone in the story or design team ever assume that some person has played Borderlands 1. You just start it from scratch.
There are cute winks at different things. For example, we have this thing where if you played the first one we detect your saved game and you get some cool unlocks.
More information can be read in the newest issue of Game Master.