User blog comment:B214/Shin DxD 1 discussion/@comment-39.51.215.62-20180720122533/@comment-28884330-20180720181929

Issei winning would be way too cheap, especially when he has just become a King and with the hint that he will lose in the semi-finals since he only needs to reach that to become Maou, and facing Indra in that round most likely. It is far more likely that he will lose in the semi-finals, the Top 4.

The arc name doesn't refer to their fight, but simply that the arc is focused on them. If it was about their battle it would have a "VS.". A connective "X" has no particular meaning hinting at a battle, and Issei and Vali fightning does not necessarily have to be in the tournament.