I don’t necessarily expect that to happen, but I didn’t see it coming when Futurama did it, either, and The Flash is way more into messing with the past than Futurama was.
Basically any moment in the Arrow-verse’s three Earth-1 series can now be retconned to include The Flash zipping through any scene in such a manner, perhaps in an effort to stop Iris’ death.
(Savitar has a shiny metal ass someone can kiss, too, for further needless mash-up talk.)
Not only for this specific crossover itself, but the introduction of this kind of instantaneous cameo could make for some interesting advancements in the future.