Loaning players out, or selling with option of buy back, are methods which Real Madrid (& FC Barcelona with their youngsters ) utilize to give "options" to their young players to find the playing time & competition needed to grow & show if they are "Real Madrid material".
Two of these players, Casemiro (Porto) & Cheryshev (Villarreal) are having great seasons with their loaned out Clubs & have shown all their talents. According to Spanish Sports media Real Madrid has decided to bring both "back home" next season both players impressed with their current evolution. Some current Real Madrid "big names" are getting on & need more rest, while the long season is often filled with injuries where both mentioned youngster will be handy to have in case to fill vacant positions.
There is a third player that has impressed Real Madrid which had to sell to "leave the nest", Alvaro Morata currently at Italian Club Juventus. The Spanish Club is impressed with the "explosion" onto the scene of their ex-player that it is said that Real Madrid is currently studying buying back the forward. Remember Real Madrid sold for 21M€ & in order to recover Morata will need to spend 30 - 35M€, plus Juventus & player will have to agree which is not so clear at this stage.
Stay tuned for developments.