A move away from C++ would probably be significantly higher-effort than the move to it- C++ can not only trivially call C APIs but can also compile most C code without modification. To support Rust would require not only porting the toolchain (though this wouldn't be too bad on current-gen, since e.g. the PS4 even uses Clang), but really working well with the console SDKs, and third-party libraries and middleware, which are all written in C++.
It would probably also be a much tougher mindshare hill to climb- even C++ took a long time to be accepted, and its standard library still isn't. Vulnerabilities are not really an issue for games the way they are for, say, browsers, since games' inputs and environments are so constrained and there's often no real consequences worse than a player losing their save file.
So from my perspective (which to be fair is relatively new to the industry) these might be the most important features for getting Rust into games:
* Visual Studio integration, including code completion and debugging. Though console support would have to come from the console vendor, anyone could work on supporting things like variable name hovering and data display.
* C++ support- though maybe different from what application developers need. DirectX (Windows/Xbox One) is all COM-based, which is strongly related. If it's handled through bindgen, it still needs code completion support.
* SIMD, inline assembly, etc. This stuff gets used all the time for performance, and for a lot of it portability is not a concern, because things are handled differently per-platform anyway.
Similarly, Rust might just not be a good fit for games because of some tradeoffs it makes:
* Games can't get by with just malloc-style memory management- and while it's easy to mess up, C and C++ handle arenas/pools/etc with far less friction than Rust, where you'd want to package up every little pointer thing behind a safe API. That's a good tradeoff here because the bugs are mostly harmless and easy to track given the constrained environment.
* Maybe error handling? (Mostly devil's advocate at this point.) The games I've worked on tend to just assert in debug mode and ignore errors in production. Carefully handling every case could legitimately be a needless time sink for some situations. On the other hand stuff like `unwrap_or` could make that much clearer without slowing anyone down.
* I don't agree with all of tomaka's points (e.g. https://www.reddit.com/r/rust/comments/616rc8/rcpp_discusses...) but they would certainly be an issue for many game developers.