Uub bowed deeply. "It is because of your patience, Master Goku. But I feel the world shifting. I feel like my training here is nearing its end."

Here is a short story based on that specific transition and the start of the GT era: The Weight of a Promise

Before Uub could answer, a pillar of crimson light erupted from the temple. The sky didn't turn black as it did with Shenron; it turned a bruised, electric purple. The Earth began to tremble, not from a physical blow, but from a cosmic imbalance.