West Brom have sacked Nicolas Anelka citing "gross misconduct" after the striker claimed on Twitter he had quit the club.
Mauricio Pochettino expects to be at Southampton next season and is looking forward to working with chairman Ralph Krueger.
Former Croatia, Everton and West Ham manager Bilic, 44, took charge of Lokomotiv last summer but could only guide the club to a ninth-placed finish in the 16-team Premier League - the club's worst finish since 1991.
A statement on Lokomotiv's official website said Bilic's contract had been cancelled by mutual consent.
His replacement Kuchuk, 53, is the former manager of Kuban Krasnodar, Salyut Belgorod and Sheriff Tiraspol.