I don't know what Gura says has much bearing, the real question is WWSD?
What would Scalia do? His explanations on NFA items run counter to the above arguements and he's continually shown a desire to reserve some rights on restrictions for the court.
Well, it's hard to say what one particular judge will do, but as far as what the court will do, Gura is 2-0, so it could be argued he knows better than anyone else.
NFA isn't being challenged anytime soon, so even if Scalia has weird beliefs in that area, I'm not sure it's relevant.
Clearly the strained rulings over the years make any kind of robust predictive model of SCOTUS decisions impossible. However, there are some trends, and I think Gura sees those clearly, and orients his actions, and chooses his arguments, so as to align with them.
One trend we can all agree on is that SCOTUS doesn't like to reverse itself. OK, if you read the Kachalsky petition for cert, you'll see each level of Gura's arguments are built on SCOTUS decisions or dicta directly, many from Heller. He's using their own determinations to herd them, if you will.
Just an example. So, when Gura says the common use test is huge, it's hard for little people like me to disagree. Perhaps we'll know more the next time Gura is before SCOTUS.