The CBA aboriginal law section hasn't taken an official position with regard to the question of an extension. What I can say is that there are pros and cons to an extension.
The Supreme Court recently, in the Carter case, commented on the very exceptional nature of extending a suspended declaration of invalidity. We do know that it was done twice in McIvor. There were criticisms made by the Court of Appeal in that case for doing so.
To the extent that court deadlines sharpen the government's attention, the concern then becomes that if it's a further six months and the substantial discussion only starts in month five, how much further ahead has the discussion really been, as opposed to having a bill pass and then a commitment to having a further one by a certain deadline? That's the motivation behind the recommendation that the subject matter come back to Parliament, either a committee of the House or the Senate, within 18 months.