I'm disinclined to believe that any AAA game will be written in Rust (one is free to insert "because Rust's gamedev ecosystem is immature" or "because AAA game development is increasingly conservative and risk-averse" at their discretion), yet I'm curious what led you to believe this. C++ became available in 1985, and didn't become popular for gamedev until the turn of the millenium, in the wake of Quake 3 (buoyed by the new features of C++98).