He wasn’t fired or disbarred or anything that might have prevented him from returning to SVU at some point.
As it turns out, Raúl Esparza left Law and Order: SVU because he felt it was time to move on, not due to creative differences or dissatisfaction with his job.
Barba is still a lawyer and clearly still feels a connection to Benson; it wouldn’t take a leap of logic for him to return.
While fans of Barba will undoubtedly be sad to see him go, at least he got a solid sendoff.