the only sense in which the relationship between C & C++ is like that of a cybertruck to a bicycle is the one in which the latter are "transportation devices" and the former are "programming languages". there is no particular feature of a bicycle represented by a cybertruck other than "it gets you somewhere".
All kinds of major projects switched to C++ already, for example GCC. All the major new projects, for example LLVM, are also in C++ from the get-go.
Even the Linux kernel is considering switching to C++ now.
Source?
considering doesn't mean it will happen in near future, because toolchains/ecosystem is not there, the same is applicable for many other projects.
Thankfully the Linux kernel development relies on testing instead.
Maybe the c++ killer will turn out to be just some future, modern version of C...
Which is bad enough but there are plenty of cases where it may do this, or it may generate short obvious sequences of code, depending on more factors like compiler flags than you can easily observe while examining the line of code in question.
Hence the "as-if" rule, which helpfully applies in a lot of places, but not all, like return value optimization. I never felt like taking the time to build the kind of C++ confidence one must require to wield it correctly.
So much so that new revisions of C are just backporting features at this point.