Wait, what? Seriously? That's stupid. That'd be like doing two Super Bowls in one year or having Christmas twice a year. WrestleMania is supposed to be THE big event of the year. Randomly just slapping another one in the middle of the year makes it seem less special.
I think that Greatest Royal Rumble was just a special event. I don't think they necessarily have any intention of making that a regular thing. I mean, I could be wrong, but I got the impression it was just a special one time deal. Mainly just to do something special because they were going to Saudi Arabia.