I doubt that will happen, but it wouldn't be out of place, at least depending on how it's executed.
It took the whole season for Rio to become a good guy, and after being the main villain for 47 out of 49 episodes, it was not jarring at all to see him become good.
Actually, finally seeing
the full roll call after being divided for the whole show was one of the most exciting and memorable part of the series.
No reason why Marvelous, Basco, and Akared reuniting as the Red Pirates again can't be just as great near the finale.