Now that season 7 has been announced we're now getting some trickles of information about it. Apparently in a tweet answered by Larson today it looks like he was not involved with writing for the upcoming season.
Haber also answered this question in a roundabout way after a fan asked if his involvement with a new show as story editor meant he wouldn't be on season 7 answering with:
His answer is a little more confusing but some are taking it as a possibility he isn't involved with season 7. I'm not too sure, so what do you guys think?
Source - Larson
Source - Haber