Roberto Firmino is still an important player for Liverpool, I think for this season Liverpool will try to keep him unless they get a high offer. The arrival of Luiz Diaz and Darwin Nunez is indeed good for Liverpool. But losing two senior players (Mane and Firmino) simultaneously is not a good thing for Liverpool.
Of course, but if Liverpool still want to look for other players in the current transfer market, then losing Roberto Firmino is also not an obstacle for Liverpool although it would be better if Liverpool were able to keep him because Roberto Firmino is a very good player at Liverpool too so it would be very wise if Liverpool want to keep it.