Joao brothers aka Felix and Cancelo looks really different when they were playing in their old teams and when they play for Barcelona, I expect Barcelona will sign both of them permanently. Barcelona need to prepare at least 200 Million Euros because Atletico Madrid tend to ask ridiculous amount.
These players fit with Xavi's tactics, they also have good supports from all Barcelona players. That's why both Felix and Cancelo can adapt quickly, they can show their best forms very early. Meanwhile, in the previous clubs, Felix and Cancelo didn't get full supports from their team mates and they also didn't fit with the tactics made by the coaches. Now, they are happy to play with Barcelona, they are in the right place to improve their performances.
I agree Barcelona should sign Felix and Cancelo permanently. But I'm not sure if Barcelona has enough money to sign both players. I think 200 Million Euros isn't a small amount of money, Barcelona probably get difficulty to find the money. Unless Barcelona can sell a few players, I am a bit doubt Barcelona can have enough money to sign Felix and Cancelo.
I assume Barcelona will ask for loaning those players back. But Man City and Atletico Madrid probably will try to sell those players with higher prices if they can play well for Barcelona during this season.