The fact that in 2020 we still don't really have CPUs that are significantly faster than those released in the middle of the decade in terms of single threaded perf (which is still the paradigm that most programming languages today operate under for the most part) kind of put a nail in the coffin of that prediction.

I can totally picture new languages as described doing well today if we had exponentially more single threaded processing power/watt at our disposal than we actually do.

I think there is still opportunity for languages that offer huge leaps in expressiveness w.r.t handling concurrency even at the cost of raw single threaded performance. Though I would not label a language like that as "slower" as it'd allow us to actually make much better use of our computing resources than we reasonably could today without blowing through most of our complexity budget, resulting in faster programs in practice.

You could argue that it's JavaScript. JavaScript had terrible performance even in 2008, can't remember now what it was like by 2010, but I would guess V8 was still pretty lacklustre back then.

I read it such that if, for arguments's sake, Ruby is 10 times slower than Java that people would start using a new language that is 10 times slower than Ruby. I'm not sure that ever described Javascript, and it certainly didn't as the decade progressed with the advancements that have been made in executing it.

I feel like that one simply missed the mark. If anything, there was greater emphasis towards languages that were more performant, even if less productive for banging out a working product.

It definitely did. IE6's JavaScript was super slow. You cannot even imagine how slow it was if you never worked in it.

Remember, IE6 was the dominate browser for years, so very slow JavaScript was the norm.

For example round about 2008 I made a client-side pivot table for a web app, tried it in JavaScript first, even trivial tables would take 10 seconds despite all the optimization I tried (in IE6, IE7 + Firefox).

I rewrote it using XML + XSLT and it was instant. But it was truly gnarly code.

I think the point of the prediction is that the new, slower language would be more expressive. More natural-language-like. That doesn't describe JS.

People who have seen more than I have: how much slower were JavaScript in IE6 vs V8?

Maybe JavaScript libraries and frameworks? I haven't touched too many of the "batteries included" ones but I see them out of the corner of my eye at meetups and hackathons, they seem unwieldy enough to fit the bill.

Well Moore's Law had pretty much ended then, but it was less visible.