First beta of FBReader Premium 3.0 uploaded to Google Play. You have to be Premium user and join the beta track to try it.
The beta includes a very first version of the built-in text-to-speech module. TTS works for text formats only (no PDF support at this moment, sorry). To run the feature, open left menu in reading mode, and select "Read Aloud".
FBReader 3.0 significantly changes the app internals. In particular, the plugin API has been changed. If you use FBReader Premium to read DjVu, you will be requested to update the DjVu plugin as well.
Read more about FBReader 3.x plans