It is not that everything should go into the stdlib, but having syn, procmacro and serde would be a good start imo. And like golang having a native http stack would be really awesome, every time you have to do any HTTP, you end up pulling in some c-based crypto lib, which can really mess up your day when you want to cross-compile. With golang it mostly just works.
It isn't really in the flavor of rust to do, so I don't think it is going to happen, but it is nice when building services, that you can avoid most dependencies.
A second tier stdlib would turn out like the Boost c++ libraries -- an 800 lb gorilla of a common dependency that gets called in just to do something very simple; although to be fair most of the Boost functionality already is in rust's stdlib.
Only when it falls short on my needs, I would drop the stdlib and go in dearch of a good quality, reputable, and reliable 3rd-party lib (which is easier said than done).
Has worked me well with Go and Python. I would enjoy the same with Rust. Or at a minimum, a list of libraries officialy curated and directly pointed at by the lang docs.