Carbon and Cpp2 are both "C++ successors," broadly speaking. However, they take different approaches in their design:

Carbon is a brand-new language that's designed to have seamless interoperability to C++.

Cpp2 is C++, just with a different syntax. (The goal is to even be able to mix Cpp2 and C++ syntax in the same source file. The initial implementation transpiles Cpp2 to C++ source code, similar to how the original C++ implementation transpiled C++ to C, rather than implementing a full compiler.)

Their overall goals appear to be different, too: The Carbon README states, "Existing modern languages already provide an excellent developer experience: Go, Swift, Kotlin, Rust, and many more. Developers that can use one of these existing languages should." With that mindset, it sounds like more of a stopgap for projects already invested in C++. In contrast, I believe that Sutter would argue that C++ still has the potential to be a viable choice for many tasks, and Cpp2 is a way to realize that.