Yeah, I suspect mainstream systems like 5e will eventually go to all system-unique religions and deities rather than using real-world religions, dead or alive. At some point, even "dead" religions, which have been revived by neo-pagan groups (even that characterization may be controversial with, say Norse gods). I have no problem in my personal games using real-world religions so long as none of my players are offended by it, but it is increasingly problematic for large, mainstream companies to risk offending those who believe in gods that are added to game fluff and mechanics.