I hope he deosn't get sold, we certainly shouldn't be that club which sells good players to bring in other potentially-good players. And I don't see us bringing in a Mbappe type of a forward anways, so no need to sacrifice him.
In 2-3 years he'll be 27-28, and I'd be happy with: Dybs, Berna, Kean in addition to one or two signings and a solid and creative midfield
Hell keep even Costa if he stays injury-and-brainfarts-free, he can perform well as a sub at 30-31 of age.