Hi
There is nothing better coming out in terms of the actual modem part, the chip designs are the same and different part numbers are usually just the same designs but made cheaper. There is no extra profit to be gained by companies like Broadcom coming out with new designs as they can't improve on what is a standard. For example no point speeding up the clock rate of the modem chip as it still can't work any faster than the standard allows. They could bring out chips using a smaller fabrication process and could then save some power, but when are you talking about analogue parts, changing the voltage the modem works at can change a whole host of other performance variables so it would need a whole new design and testing process and there isn't enough money to be made to justify it.
So stick with what you have, nothing better to replace it with if it isn't broken.
Regards
Phil
