Stupid, stupid, stupid, stupid idea.
Want to see less decisions? Make the fight one ten minute round, or one ten minute round and a five minute decider (Pride).
Want to see more decisions? Make the fight so long fighters are scared to exert any energy.
Fighters who do normal training camps are gonna have to dedicate extra time now to cardio and therefor less time to technique and improvement.
This is only a good idea if the extra two rounds are optional, only implemented when there's a draw.
edit: to answer to HexRei, fights are rarely finished in the fourth round, and you know how many fights have been finished in the fifth? Four. Ever. And one of those was just because of a cut.
sig credit to Limba