Interestingly Scala has come from Academia, Industry, and Hobbyists. And for me it's already the next great programming language. Yeah, it has some warts and is hard to learn but that's true of all great things. :)
That's an interesting point. The slide implies there will be no next great programming language because academia nor industry nor hobbyists can deliver it, but overlooks the possibility of a combination working together. For example, Rust started as Graydon Hoare's hobbyist language and then development was sponsored by Mozilla.
Now, whatever innovation this proliferation of languages may bring, it also brings fragmentation which acts as a counter-weight on the value created for the industry as a whole.
Whether the net effect is positive or negative is very difficult to tell.