Barcelona may be planning to release Dembele or Griezmann. But I was saying that Atletico would be stronger if Grismann will join. And next season Real Madrid is forming a very weak team compared to the previous season. So with Griezmann in the squad, Atletico Madrid's chances of winning another title will increase.
Dembele wants to be released? I'm not sure about that and so far it's still a rumour. Even I'm not so sure Griezmann will leave Barcelona to return to Atletico and I'm sure he will stay at Barcelona. As for the chance of winning, I firmly believe Atletico will not be able to defend the La Liga title last season and reclaim it next season. Barcelona and Real Madrid are tough competitor for them, and I feel that if it's not Barcelona then Real Madrid will win it next season.
I haven't heard rumors of Dembele leaving Barcelona. But Barcelona will have to releas either Dembele or Griezmann. Griezmann does not want to leave Barcelona now and he has already announced that he is willing to reduce his salary. So I think Barcelona can sell Dembele.
On the other hand, I don't see Real Madrid as a title contender now. They have lost some important players in their team, new coaches in the team. Real Madrid have yet to sign a replacement for Ramos and Varane.