I would expect any lower federal court to uphold just about any ban, registration scheme, license fee, etc. that the elected politicians manage to pass. The chances of SCOTUS taking up a case that doesn't represent an effective outright ban on possession of ANY/ALL firearms is close to zero.
Doesn’t that depend on how many conflicting rulings we get from appeals courts? Every time two Courts of Appeals make conflicting rulings, it becomes a potential SCOTUS case to resolve. All we need is one Court of Appeals to overturn a ban on assault rifles in any state, and that will conflict with those upholding the bans. Presto. Off to the Supremes.