According to Sports Business Journal ($), the NBA is proposing lowering rookie salaries by 30 percent in the next collective bargaining agreement. In a bilateral bargaining arrangement (monopsony league and monopoly union), taking from not-yet union members might seem to be a favorable proposal. Even if current players might agree to such a policy change, I think the NBA might want to reevaluate this strategy. With the rise of professional basketball around the world, some of the best young players may choose to play in European leagues where their salaries are not restricted, just as Josh Childress (formerly of the Atlanta Hawks) did.
More American ballplayers jumping to Europe only makes further jumping easier. And sponsors eager to spread their brands worldwide may be willing to subsidize player moves outside the US. The NBA doesn’t have the market power it once did, largely thanks to its own successful promotion of the game internationally.