Rabiah
One of the earliest planes visited in MTG, we’re pretty much guaranteed to never re-visit Rabiah. Because we’re already there. Kinda. Rabiah is set in a fictional Earth that you’re probably very familiar with. The whole plane and Arabian Nights set was based off of the tales in the classic book 1001 Arabian Nights. Sure, there’s lots of magical creatures and spells, but it’s also existing IP that is used elsewhere by other companies. Wizards has left Aladdin behind.
Rath
Wizards of the Coast
Rath is a popular plane that folks liked a lot and that Wizards has placed many Magic sets in. Originally the plane was a hit because it was one of the very first times MTG left Dominaria. People loved it because it was something new, but as Mark Rosewater himself states, its world building doesn’t hold up to modern standards. (No pun intended.) Plus, during a battle with the Phyrexians, it got “overlaid” onto Dominaria, which means the whole plane got squished onto the other and the two are basically one and the same now. So does that mean we actually have gone back to Rath in Dominaria United?