I haven't heard that it's been "removed." Just that it's not important anymore. Really, the only reason the Blood War even existed was because the designers were straining for a way to establish the Devils and Demons as seperate forces.
But now they've better established that distinction. The Devils are angelic traitors trapped in their dominion. The Demons are corrupted primordials and elementals (who were already pretty bad to begin with). And the concession to just two non-material planes means their positions in the cosmos seem less arbitrary but opposed, instead of just being the "law aligned plane, lol" and "chaos aligned plane." Which both sit right next the good, evil, Jim, astral, shadow, earth, water, wind, fire, and heart (by your powers combined) planes.
They'll surely go to war at some points or another. They just need to have a reason for it, now.
Though I do kind of miss Tanar'ri and Baatezu.