I really doubt Xavi will do this though. I think his heart is set on someone like Bilva with a like-for-like replacement for Busquets dropped in next season.
City didn't seem very interested in taking him either and maybe he really is such a niche player than neither Pep nor Xavi think they can get the best out of him in their 4-3-3s.
Barca have Pedri / Gavi readymade to take on those roles in 2-3 years, they just need a DM. If Barca switch to a 4-2-3-1, they'd have to play a proper #10 (no idea how Pedri will do in this role), Gavi will be left out and they'd have to start Kessie / FdJ.