One is most probably Azerbaijan (L-39), another could be Spain (F-5 and C-101), and the last maybe Pakistan (JL-8)?
I'm not sure if Pakistani JL-8 needs a replacement already though. Sure they have Jeff, but Jeff is a proper LWF. For it to replace the JL-8, they would probably need to develop a separate, dedicated AJT/LIFT variant like how the Taiwnese developed Brave Eagle AJT based on Ching Kuo.
Malaysia (Hawk) also comes into mind, but they already have FA-50 on order, so doesn't really make sense.