BlueSkyStar – a developer responsible for many sound packs, especially for Airbus add-ons like FSLabs, FlightFactor or ToLiss. Today, the developer released an unofficial verison of the IXEG 737 Soundpack for X-Plane 11.
The developer said that this is just temporary soundpack until he releases official one. In the Facebook post, the developer describes how to install the soundpack. You have to replace the old sounds in X11/Aircraft/X-Aviation/IXEG 737 Classic/Sounds.