It is not about optimal performance. Ruby, or specifically MRI here, is anywhere between 20-100x slower. And there are other dynamic languages that is much faster then Ruby. If Ruby is only 2-10x slower no one would complain. But right now it is so far off the chart that is why you see a shrinking usage of Ruby.
So when the plan will be realized, it would be these 2-10x slower than others.
The article clear states that, as well as numerous other sources Ruby 3x3 means Ruby 3.0 will be 3 times faster. The problem is it will be 3 times faster then 2.0, and we already have 30-40% speedup from 2.0. So for Ruby 3.0 is likely only 2.2x faster then Ruby 2.4.
2.2x, in the grand view of things, is still very slow.