I don't think that condition will come to exist. The federal courts are almost perfectly uniform in their hostility to the RKBA.
Even if there is a split between the Circuits, SCOTUS can "wait" to act. It has no obligation to settle splits, and it might view a split on an assault weapons issue to be unimportant.
And finally, if it DOES decide to take up a "certain weapons" ban, it is more likely to uphold it, than to strike it. The only protection I see SCOTUS giving is against outright complete bans on possession of civilian-style long arms and sidearms.
What we get from liberals is just more Midnight Basketball, and the Court is no different. They are so behind reality and will never catch-up with it, I'm afraid.
Society IS changing but our Constitution must be held in chains else people will take it upon themselves to solve immediate problems with rights explicitly given to them. Those same Koreans who once stood on rooftops in Los Angeles to protect their businesses from rioting masses with SKS rifles would go to jail as the SKS was banned in CA a while back.
Perhaps this court would allow them to be inside the building with a bolt-action hunting rifle but this might not be the best logistical position. "Basketball, anyone?"
So, when someone's wife is shot dead in a parking lot and her car jacked, perhaps we could get a special edition B-ball, signed by the Justices themselves, delivered by UPS to the grieving family- at Midnight.