I found out a few interesting things that may interest people, regarding foreign carriers at Belgrade Airport.
Aerosvit will continue with their weekly service from Kiev with the 735.
Alitalia will fly daily from Milan with the ERJ.
Alitalia will drop flights from Rome, thus JAT will be the only operator on the route with 733s.
American Airlines will codeshare with Swiss from Zurich.
Austrian Airlines will fly twice daily from Vienna.
British Airways should fly four times weekly, primarily with the A320.
CSA Czech Airlines will continue from Prague with ATRs and 735s.
Lufthansa will open daily CRJ flights between Frankfurt and Belgrade.
Olympic Airways will continue with ATRs from Athens.
Snowflake should continue from Copenhagen and Stockholm with 738s.
Swiss will continue with their daily service from Zurich.
Tunisair is destined to open a twice weekly service from Tripoli.
United Airlines will codeshare with Lufthansa on the Frankfurt flights.
Uzbekistan Airways will continue with their service from Tashkent with the 763s. JAT should continue their codeshare on the flights to New York.
I am sure that I forgot a few companies, however that is it in a nutshell.