To me, it really comes down to this. We need a massive improvement from the offensive line next season and keeping project offensive linemen with "maybe" potential on the roster is just not worth the gamble.
It is rare that a project offensive linemen ever develops into a dominant starter. At best, they will end up a solid starter, but the chances of that are rather slim. When you have a solid starting offensive line, you can afford to keep one or two project offensive linemen on the team, but we don't have that luxury. Now if Arkin can be put on the practice squad, then perhaps they can keep him around a little longer. Otherwise, I just don't see the Cowboys keeping him around.