User blog comment:B214/Season 3 confirmed!!!!!!/@comment-107.10.155.255-20141231191354/@comment-1359322-20150106224537

You do realize that it might....actually it'll just be part of the opening. Just like how the first opening had Ise vs the 3 Fallen Angels and Ise vs Riser. The second opening with Ise dress breaking both Xenovia and Irina. The third opening with Rias vs Akeno.

The anime opening has a tendency of adding all this bits of random fights in it, maybe the anime producers just felt that placing Ise vs Sairaorg on the opening is a good way to introduce Sairaorg. Or they wanted to add a fight that won't risk spoiling the plot in season 3 thus the Ise vs Sairaorg bit.