White, Gabriel, Saliba and Holding next season seems right to me in terms of quality, needed game time, age profile.
White and Gabriel likely go into next season as the starters, with Saliba pushing hard and getting lots of minutes, whilst Holding will hopefully be content with cup games and coming in as cover.
Three that can interchange because they each could be starters and one reliable squaddie looks right. Comparable to Liverpool with van Dijk, Matip, Konate and Gomez, and City with Dias, Laporte, Stones and Ake.
And our trio of 'starters' will have a ton of potential, too.