That doesn’t answer the question. If Congress can “constitutionally regulate the interstate commerce of particular weapons”, what prevents them from incrementally regulating out of existence the ability to obtain or own any kind of firearm at all? According to you, nothing in the Constitution.
Mainly the people/the voters.
The courts could rule that there is no compelling state interest to prohibit a certain class of weapons. Or that the law is too broad. The states could claim their ability to form a militia is infringed. If gun crime increases, the law could be challenged on a public health/public safety basis.
But I see the government going in the opposite direction on gun laws. The federal AWB was allowed to expire. More states are allowing concealed carry. More states are passing "stand your ground" laws rather than "retreat if possible".
I'm more concerned about the erosion of our 4th amendment rights.