What Would Palpatine Have Done If He Could Get Into The-World-Between-Worlds In Rebels?
If you watch the scene, the same portal with Kanan’s death is the one the Emperor is in, so I’d bet dollars to donuts he was luring Ezra with that.
Of course, even though he tries to force his way into The World Between Worlds, he is stopped and Ahsoka and Ezra escape, giving him no foothold to grab onto.
Had he entered, well thats just about his endgame realized.
Unlimited power, exerting his dominance over all of space and time at once, the galaxy his play thing for every second of every era!
Even the power of The Death Star would pale in comparison: that was but a tool to keep the galaxy pacified so he could be absent to pursue the leads on esoteric sith pursuits such as this.
Even the most powerful of Sith Lords and Jedi Masters would be nothing to an individual who could reach in to any point in time to influence their life just for pure visceral enjoyment and sadistic thrill, let alone the lives of every individual in the galaxy.
No one would be safe from his tyranny, a god above gods, to ascend far above every other person and force-user that had ever lived.