The only thing that upset me about the DB was that they have fallen so far away from what they used to be and you don't really get a chance to fix it. They don't abide by the 5 tenants anymore, and Cicero is the only one that believes in them. Sure, you get to be the listener and do the Night Mother's bidding, but the rest of the DB still goes off killing people without her blessing.
I just killed them off in my second playthough because they're barely a shadow of their former selves.
But if you play through the whole Quest line, then when you take over at the end, it is heavily hinted that you were chosen as Listener to not only rebuild the Brotherhood in Tamriel, but to also return it to the Old Ways. The Night Mother is speaking again, Sithis will be regularly getting Souls again (as is his due. Hail Sithis, Hail the Dread Father!

), and your character and Cicero are going to be schooling and rebuilding (with help from Nazir) based upon the Old Ways and the Five Tenets.
The Dark Brotherhood will be back and better than ever, that's pretty much a guarantee.
BTW; if you need a Sneaky follower who is also good at ranged and close combat, go with one of the DB recruits once you open up the Dawnstar Sanctuary. Those little bastards are
amazing! And then iof you get them to close to your level with the Wabbajack... nothing will ever stand against you again.
