I'll use the definition that an ultimate is a loyalty ability that costs more loyalty than the planeswalker starts with. By this definition, two of our eligible decks have planeswalkers with ultimates - Kaito Shizuki in blue-black, and Elspeth Resplendent in white-blue.

Will anyone use one of those planeswalkers' ultimate ability in a game that is part of the tournament?

This market depends on reports, and the burden of proof is on YES.