It all depends on what the CFTC decides on what the "effective date" of implementation is, it could be effective immediately once they get the votes needed or maybe at the start of the new yr, etc.
After the fiasco that MF Global caused by using client funds I would bet the farm that it will be implemented immediately.
The day after news broke out about the MF Global scandal, I got hit with a swarm of calls and emails from frantic clients wondering if their futures broker could do the same to them. Passing this law won't guarantee absolute compliance from irresponsible brokers, but no doubt they will think twice about touching client funds for their own speculative use.