I like Go. The language is sane and small, the standard library is great, and the tooling is nice, the community is getting quite large. It's a bit too high level for me to call it a C successor, but I get similar joy from coding in it as I do with C. It's just so clean and neat, and I still get native code, and with no dependencies either. Pretty great. Go is so good thanks to the sum of all its properties. I think it will be around for a long time.
I'm not too much into Rust, but sure, if you absolutely cannot have even a low latency garbage collector involved or do very low level work like drivers, I guess it is useful. As soon as I don't, I feel like the pragmatic nature of Go is very appealing. I wonder about Rust's future, where it will be in 5-10 years.
I'd prefer Swift more if stuff started happening here as for cross-platform support. I hear the Linux support isn't even quite there yet, and as for Windows, it just recently saw _any_ kind of progress. I feel like it will take a long time until Swift feels like a natural general purpose choice across the largest three operating systems, rather than an iOS / OS X development platform ported to said platforms. But sure, Swift as a language feels modern and just great. Sometimes like a merge of Rust and Go, with the similar focus on safe code of Rust from guards, optionals, seeing the good in immutability, pattern matching. I wish Swift was much more popular and with much better cross-platform support.
I have played just very little with D and it has a bit much feature creep and bad traction for my taste (community _does_ matter). It had a chance of becoming more popular before, but I can't really see it anymore with these new languages. They already seem to have overtaken it in popularity, leaving D as a used but very niche language.