That's a good question. Rust is going to face this situation continuously. There will always be lots of choices. I hope that the relationship between crate authors will be friendly.
When you say "our" I take that to mean "the rust project".
Personally, I want to encourage the most people to write the most and best Rust crates possible, for the ecosystem to be vibrant, and to evolve.
In the case of log for example, I doubt anybody is really in love with that crate, so I hope there will be other solutions. slog looks excellent and people should use it.
Regarding splits in the ecosystem, I think they are sure to happen, and we should expect it and expect to deal with it. We're still pretty much in the middle of the rustc-serialize -> Serde transition, but a rustc-serialize -> Serde post-mortem could make an enlightening thread. Do you see the rust-serialize / serde situation as problematic? My impression is that the situation has been pretty understandable and not so horrible, at least if one's expectations are suitably tempered.
I think we should do our best to walk a fine line between encouraging a proliferation of great Rust crates, and also working to make Rust crates more interoperable and discoverable. I think we can learn how to manage versioning and transitions in the ecosystem in a way that is reliable, and is also tolerant to change.
At least with respect to the log crate, I'd prefer not to add structured logging. My feeling about log is that it is mature and doesn't change much, so let's polish it up for 1.0 and be done. From there interested parties can regroup to think about future directions for logging in Rust. Maybe that leads to log 2.0, or a shift in focus to slog. That's just my opinion, as someone who hasn't maintained any of the log crates. @sfackler or @dpc might have opinions.
I suspect it can, but @sfackler would know better.