Regarding RM's depth in midfield.
First of all, i think he will stay at Betis next year hence the 6 year contract. Secondly, James will be sold, Modric is getting up there in age. Depending on what you believe from the press Kovacic might also leave.
Considering these things, in the next 2 or 3 years they could have Kroos, Isco, Casemiro, Llorente and Ceballos as mid options. If i'm wrong please feel free to correct me. While still impressive, it's not that stacked in numbers. It's what an elite team, that plays 60 odd games a year, should have.