As far as consumer engines go anyway, Lumberyard is the only product I know of that will have this.
A couple of things to note though, because of Amazon’s stance of not wanting to see voice acting jobs disappear, this will not become a final quality dialogue generator and should be used only for placeholder sounds. This also is coming into the engine as one of their so-called “cloud gems” (so it will not surprise me if developers will have to pay to use it).
In all, this is turning out to be an interesting engine, but I will caution that a time may come where if you want everything that’s not part of a base toolset, it will turn out to be an expensive subscription-based product (did anyone really think that such cutting edge tech. would be free with no catches)?
Still, text-to-speech may eventually become a boon for small studios who don’t have the money to attract top talent for acting, but we are not there yet (but don’t say we won’t be).