I agree with AvalonAurora: They should do both.
Real-world basis has been deep rooted in MtG since it's creation, such as with Arabian Knights & Portal: 3 Kingdoms. Not to mention the fact that much of high fantasy lore is based off of mythologies from various ancient cultures, such as Minotaurs & Medusas from Ancient Greek Mythology.
There is a lot of lore hidden within real-world folklore, & many of which are not common knowledge such as "Leanan Sídhe" in Celtic folklore or "Baba Yaga" in Russian folklore.
I think the main reason why WotC have been focusing on real-world settings is because of player-demand for them. There was a big push for an Egyptian-like world, hence why Amonkhet was created.