Hampson is withdrawing for personal reasons, his New York-based representative confirmed.
The program will include Rossini's Overture to L'italiana in Algeri, arias from Mozart's Don Giovanni and La clemenza di Tito, extracts from Wagner's Flying Dutchman and pieces by Berlioz, Tchaikovsky and Glinka. Jirí Belohlávek conducts.
Terfel, whose recent London appearances include Wotan and Wagner's Dutchman, will soon be seen as Gianni Schicchi at the Royal Opera House.
Graham was last seen in London at the ROH as the Composer in Ariadne auf Naxos; she also appeared at the Proms last summer performing Chausson's Poème de l'amour et de la mer.