I'm really looking forward to those actually being available to use.
I've just started to use AWS Polly in some demos, but the speech synthesis quality feels 2-3 years old at least :/
I think what's missing is to understand and adapt the speech rhythm and pauses based on the language. At first sight I would say that this requires human intuition, but then again, lots of literature is repetative, so I think ML could actually work quite well well, with actual understanding of the text, given enough data.