Felblood elves betrayed the Sin'dorei, attacked Silvermoon City, took over the Sunwell and almost succeeded in summoning Kil'Jaeden to Azeroth. They also bathed in demon blood to turn themselves into demons.
Now, a few years later they are supposed to come back knocking at the gates of Silvermoon, say "Weve sowwy" and be accepted back into Sin'Dorei society? It's more likely they'll be flayed alive if they ever step on Azeroth again.
Next you'll propably suggest adding Eredar as a subrace for Draenei.