Pacquiao's Ability To Reinvent Himself As Boxer Will Sustain Career

At some point, the punches lose some of their sting, the hands some of their speed. Guile eventually has to replace brute force, savvy displaces the athleticism of youth. Realizing this is half the battle—the other half is accepting and implementing the changes successfully.

And it would appear that Manny Pacquiao has done just that.
While it's hard to see Pacquiao elongating his career well into his 40s a la Bernard Hopkins—Pac-Man has too many other interests and responsibilities for that—he proved once and for all against Timothy Bradley that he has reinvented himself as a boxer, and it's a look that suits him well.
Nigel Collins of ESPN has more on the transformation:

All of the ancillary activities are rooted in Pacquiao's boxing success, and now he is attempting the most difficult challenge of his fighting career: a metamorphosis from whirlwind knockout artist to savvy boxer. It's a transformation only the very best can accomplish, but when they are successful, it can extend their careers and keep them winning well past the point where sticking with their original style would have sent them prematurely shuffling off to Palookaville.
When he could no longer float like a butterfly, Muhammad Ali came up with the rope-a-dope and other stalling tactics to preserve his energy. Bernard Hopkins understood that he was getting too old to punch it out with the best young studs in the middleweight and light heavyweight divisions and figured out a way to win by taking away what his opponents did best. Marco Antonio Barrera held off Father Time for a handful of lucrative years by ditching his macho style and using his neglected boxing skills. It's simply a matter of adaptation or extinction, and Pacquiao shows every indication he's striving for the former.

There will always be disappointments in regard to the latter part of Pac-Man's career. The knockout against Juan Manuel Marquez and the loss to Timothy Bradley—albeit a controversial, perhaps unjustified loss—will always be a dark period. The failure to negotiate a fight with Floyd Mayweather, denying the sport what would have been its biggest fight arguably in decades, will remain a stain on his legacy (and Mayweather's, too). But Pacquiao seems determined to not only leave the sport on his terms eventually but to also do so when he's still one of the top boxers around, even if he long ago stopped being one of the most fearsome brawlers in the sport.
Not to say that Pacquiao was ever a blind puncher—his ability to come at opponents from odd angles and the speed of his hands were always trademarks. It's just that they were the prologue before he sent an opponent to the mat or sucked the will straight out of him with his powerful blows.
Now, he has to beat an opponent with his mind before he can beat him with his fists. It was a lesson he had to learn the hard way against Marquez. Against Bradley, it was obvious Pac-Man had taken his lessons seriously.