I remember reading that the 4 class config 772s are being replaced by the 779s, and the 3 class config 772s and LGW 772s being replaced by the 78X

Current 772 fleet:
4 class 772: 18
3 class 772: 13
LGW 772: 12

On order:
779: 24
78X: 32 (excluding the 6 that are arriving this year and next)
A35K: 6

After replacing those, there would be 6 779s, 7-11 78X and 6 A35Ks for expansion, 19-23 in total.