NVDA 2015.4 has just been released:

http://www.nvaccess.org/post/announcing-nvda-2015-4-release/

Users of Acapela TTS for NVDA can just upgrade to the latest version of NVDA 2015.4 without need of performing any operation. The Acapela TTS for NVDA plug-in will start working without any issue as soon as the new NVDA version has been installed.