They did announce they had no intention of adding new vault hunters, it was lay over from two factors that popped up in Bl2 and have carried over in to BL3. BL2 only launched with a single new game plus then had I believe two additional modes added alongside along with levelled bad guys and higher level caps for the players. The issue was that the game was, specifically the original Vault Hunters were never balanced to go up against these new higher level, buffed enemies so they quickly got out matched and became near unplayable (not sure if they ever balanced this) This is were the new vault hunters came in, Kreig and Gaige were balanced with the higher level caps in mind so quickly became the default characters for players wanting to play the additional vault hunter modes. With BL3 they wanted four characters that no matter what, worked across all levels and were chosen according to the player's play style rather than one being better or worse than another. They spent a load of time balancing level caps, skills and bad guys to try and encourage this it is also why the new level caps have only add 3 or 4 levels each time. The amount of work that has gone in to balancing the vault hunters vs levels vs enemies vs level caps and ALL the various stats and factors from weapons and shields is why they have said they won't be adding another VH, just to much work. I mean they are still tweaking and adjusting skill trees, weapons, etc even now trying to balance things out.