Starting to wonder if this is FlyerTalk or A.net with all of the misinformation and armchair pilots saying it's InHeReNtLy UnStAbLe
This is a great opportunity for Delta to lower their costs. It really just boils down to that. Lease costs, maintenance costs, cost of new airplanes down the road, etc.
If Delta gets the MAX, then eventually major airline in the USA will have some variant of it (AA, DL, UA, WN, AS... even North America if you include AM, AC, and WS). So good luck finding another way to get where you need to go (unless it's one of the like ten places JetBlue flies to or you are willing to take a ULCC).
-J.