He's only on loan there, the Ducks can bring him home at any time. I believe this is also a part of the contract with Färjestad.
But Färjestad's coach continues to say it's part of Solberg's development, full practice but less games for a while because of his young age. Senior players are ahead of him, and now all injured guys are back. So it's not because they think Solberg is a bad player, and they will not send him to a lower league like the J20.
That being said, personally I think the AHL would be a perfect league for Solberg, fits his style much better. There he can deliver big hits and fight as much as he wants while playing well as an offensive d-man.