#2 Might Not sign with WWE: A lack of creative control
When it comes to pro wrestling promotions, no one is better at developing, marketing, and tweaking athletes to make them into megastars than the WWE.
The WWE is very much a huge corporation dedicated to producing talent that not only can wrestle matches but can also move merchandise and generate mainstream media attention. There are costume designers, musicians whose only job is to create individualized theme music for each wrestler, and road agents who are constantly working with the talent to make them just a little bit better.
However, that much attention can be a double-edged sword and cut both ways. While the WWE can make stars out of little-known talent, they sometimes also change some wrestlers too much and the crowd can no longer sympathize with them.
Given that Kenny Omega is very involved with creating his own ring gear, theme music, and the way his matches are booked, he might not want to jump ship to WWE, where there will be a ton of outside influence on all of those things.