Bloodborne was always going to be a hit, but even Sony was surprised by just how briskly it sold. It appears it’s outdoing even the previous Souls games… and we all know what that means! Back to the well with you, From Software!
On one level, this isn’t a surprise. Dark Souls II had three DLC campaigns that, in retrospect, were test runs for Bloodborne with their elaborate traps, areas changing over time, and defeating bosses unlocking new shortcuts and making old areas different and more dangerous, and they actually got more critical acclaim than the base game, due to being their own thing.
On other… where’s it all going to fit? Yharnam is a puzzle people somehow lived in, filled with hidden areas and elaborate shortcuts. Part of the fun is finding an elevator and figuring out how to activate it, but as a result, one or two bits aside, it means by the time you’re done you’ll have explored the whole joint thoroughly and you’ll know where everything is. Everything fits together with everything else.
They’ll likely do what the expansions did: Just warp you to a new environment and leave you to figure out the plot for yourself. Certainly there has to be more to the Nightmare Frontier. We’ll likely learn more at E3.