I don’t think the NBA stands to gain quite as much revenue windfall as they’re hoping, and certainly it won’t be in one big rush to create a true spike. Their primary hope for a revenue windfall comes through convincing states newly enacting gambling legislation to give the NBA a small percentage of the money bet as a so-called “integrity fee.” Firstly, legislation takes a while to pass in each state, so even if they were successful in getting this integrity fee, the new revenue streams would not come all at once, but rather would enter over the course of 3-5 years.
Secondly, cash-strapped states (in other words, all of them), are looking to tax gambling revenues as a source of new income that no one will complain about, helping them with their budgets. Giving the NBA a cut is going to come in part from state coffers, and most states aren’t going for that. There might be a couple that do fall for it, if a well-placed legislator sneaks in some language, but big gambling revenue states like NY and CA will not (and in the case of California, if they do, it will be reversed quickly by a voter initiative within a year of the info becoming public).
The NBA is asking for a 1% fee on all NBA bets, which they calculated as being worth $2 billion. That’s simply not happening, and they would be lucky to get a tenth of that.
However, they will find new advertising partnerships available with gambling institutions that will see the NBA as highly synergistic, and should be able to profit off that, but I doubt it will be nearly the magnitude that owners are hoping for, and again, it won’t arrive all at once. That said, you’re right that future cap and tax thresholds after the one set next summer will rise more than they otherwise would have, and that will dull the expense of contracts signed this summer and next.