Going by some of what Randy has said, it would seem he wants to put Borderlands out to pasture along with the Gen-7 consoles. He wants to move on to new IPs. That's what I think is most concerning. Borderlands is their lightning strike, their one real hit. They've had several misses, and killing the golden goose can't be good for them, let along the many fans of that game design and universe. While preventing sequelitis may seem like a good goal to some, I think good videogame concepts need and deserve more than a couple of iterations to develop fully.
The more I look at it, the more this project looks like DLC that got too big for a game pushed to its load limit already, and needs to be released on its own. Probably more profitable at a standalone price too, since the diehard fans will likely be its largest market.