I think it would be a great thing, in a No. 1 Contender's fight! because winner of that would eventually have to be ready for a five rounder!
But, i son't know about the other fights! Even if their on the main card!
You can judge it either way:
Imagine 2 more rounds of in the Torres - Banuelos fight! That fight wasn't entertaining at all. At least for me!
On the other hand - Franklin vs Wanderlei, 2 more rounds!!! Heavenly!
I think if the UFC were to make that happen, they would have to be more careful on who they choose to fight on their main cards!
In the end - i like the idea!