cr:1.8.10

If an effect specifies “your next attack” but does not specify how the player gains control of the attack, it refers to the next attack that is played, activated, triggered, or otherwise comes under the player’s control, and the effect applies to the attack at that time.

Example: Prismatic Leyline has the text “Your next red attack this turn gets +1{p}, your next yellow gets +2{p}, and your next blue gets +3{p}.” If a player plays a red attack with stealth, it will get +1{p}. If the red attack is replaced with a blue attack using Uzuri’s activated ability, the blue attack will get +3{p} as it is a new attack that comes under the player’s control.