imo, you have to play a few games at the higher level and see how you do.
The gap between Immortal and Deity just got bigger, by the way. I think it's likely that under some setups (civ choice, map size, speed, enabled victory conditions) you'll be winning Immortal consistently but completely unable to compete at Deity.
I suspect the same is true for the step from Emperor to Immortal, not sure yet.