Regarding Joao Felix and Cancelo, if they can be consistent with their performance, it is very likely that Xavi will try to make them permanent at the end of the season. It could be that by releasing several other players, it will cover the costs of recruiting both or one of them.
City want to do away with Joao Cancelo, just the same way Athletico Madrid want to sell Joao Felix, but the problem is the wages in their contract and the signing fee that the two clubs would request. Barcelona are in a financial mess, thus i don't think they can cover all these and make it work, even if they release a few players. There is a pretty high probability that the both players will return to their clubs after the loan spell is over, and from there the club will prolly work on their exit to clubs that can afford them.