Maybe in 4 or 5 years, if things go well. There hasn't even been a 1.0 release yet. That's the bare minimum necessary for a lot of existing C++ users to even consider Rust as a potentially viable option.

Assuming Rust 1.0 is released sometime this year, it'll still take a number of years before Rust even begins to offer the very wide range of libraries/frameworks that are available to C++ developers.

Interfacing with these existing C++ libraries/frameworks may speed things up, but at that point its disputable whether it's really Rust being used.

Rust may be among the most promising alternatives, but it's just not there yet, and won't be for some time.