User blog comment:B214/Question and Answers 2/@comment-187.209.0.247-20140225185340

Currently Issei demon power is almost CERO, currently issei even can not fly with his demon wings, this are lines from VOL14 when Draig was sleeping and issei cannot use his scale mail and activate Jet Wings:

'''I make the magical ship—Ryuuteimaru appear, and grab onto it. Ryuuteimaru continues to fly around while having me hang onto it. Oh, it has an amazing horsepower and strength despite having me hanging onto it! I’m ashamed I can’t fly with my Devil wings in my base form……but I will leave my support to you, Ryuuteimaru!'''

Even if issei has 4 Mutated Evil Pieces + 4 Normal, his demon power is so low, and also the fact that he is training to Manipulated the Holy-Dragon-Killer-Aura from Ascalon. So there is a possibility for the True Longinus.

And also the fact that the next Vols are for Irina and Xenovia, something related with the Church and the Angels. So i think is possible.