The only decline with boxing is in mainstream coverage with in the US, something the UFC gets more of with the casual fan/guys who buy tapout shirts. Boxing is still globally superior than mma, especially in places like Mexico, the UK, etc.
Not enough young up and coming stars, which is why Oscar (who hasn't beaten a top ranked fighter since Vargas) is still their best draw. It's time for a new generation to cary on...... with Bernard Hopkins
Manny/Ricky Hatton will be huge, and will kill anything the UFC puts out this year