Bloomberg will not give up. The courts, Exec Order's, and elections are all in play. The stupidity resides in the unenforceable nature of the law. NV, like most other western states, has no way to tell who owns a given gun. There is no registration archive to call on. As long as the individual says "it's my gun" they can't prove it isn't. The same bill is already on the ballot in NM, probably based on the passage in NV. Perhaps his strategy is to attempt to pass a "mandatory registration" law in every state just so the transfer law can work. "Hey, you voted for "A", but to make that work we need "B". He may go for a registration with the Fed's too.
In the event the Obama EO doesn't happen, the current Federal Courts will uphold it, and require the FBI to extend Brady Checks. The NRA will use this as a prompt to press for Instant Check expansions, and promises that the records are destroyed provided they are not an unfunded mandate. Having obtained political cover, Trump will back these changes, as long as they are relatively inexpensive. The Democrats will agree with added data sharing from health-care providers & insurers. A deal will be struck.
I can see Obama issuing an executive memo to the FBI, instructing them to conduct the checks, on his way out the door. On the bright side, that would also be a good first test of Trump's new found appreciation of RKBA.