It helps that Go is a relatively new language and the easier optimizations are getting taken care of. I doubt we will see this much of a performance gain from another 1.* release. There are definitely significant improvements to come, but I don't believe it will be this substantial.
They are still working with low hanging fruit. Brad Fitzpatrick mentioned his optimization method was to run the profile, and pick the thing on the top to work on.
Isn't that the standard way to decide what to optimize? There's often not much gain to be had if you are optimizing things that are not the bottleneck.
Rob Pike said that he believed that they could get similar performance enhancements in the next release. He was talking at Google I/O fireside chat on Go.
