Does playing Sett trigger Volibear's effect?

Ruling: No, playing Sett does not trigger Volibear's effect. Sett enters as a 4 Might unit, and by the time Sett's triggered ability resolves to make him 5 Might, Volibear's window of activation has already passed.

Sequence:

• Sett enters the battlefield as a 4 Might unit
• Volibear checks the unit's Might value at this moment and sees only 4 Might
• Volibear does not trigger because the condition is not met
• Sett's triggered ability then resolves to buff him to 5 Might

Nuances:

• Cards like Draven Showboat would trigger Volibear if you had 2 or more points, because they enter with the higher Might value already applied