Well, rumour has it he's kind of a doucher and a pest in the locker room and that Brynäs might move him down to an affilliate. Don't take my word for it though. But the fact of the matter is that he hasn't really develloped as well you would want him too so the affiliate roumour might have some substance to it.
Honestly I think he should go to the AHL to get proper development, but maybe he doesn't want to take that step yet. He's a big physical skilled kid, yet seems to be pretty much last in the pecking order from the Brynäs' juniors to get a chance. And he's not subject to be moved by Brynäs afaik since his contract expires. If he's not getting a spot with them, he'll sign elsewhere and not re-sign just to get loaned to Allsvenskan.
But I agree, something feels like amiss. Joachim Rohdin, an undrafted winger two months older than him is on the team and signed an extension over next year, while Rensfeldt isn't on the team and hasn't signed.