Barcelona might not be a rival in Laliga, and it is impossible for them to be a rival in UCL for Real Madrid. Real Madrid might make it to the finals, that is if they are not being kicked out in the group stage. However, the chance of that happening is slim. Manchester City should be able to go far next season if they did not clash with Real Madrid early like this past season.
I hope to see a different club in the finals if any of these two clubs did not make it to the finals. Next season is hard to predict with the current informations on ground. I want to see that different club apart from Real Madrid and City that will surprise the world just like what Dortmund did.
We can see this because, as has happened so far, there are quite a lot of surprises in the Champions League, although it cannot be denied that the strength of Manchester City and Real Madrid is above average, so one of them is likely to reach the final, but I believe in the surprises that occur in the Champions League, everything will not be easy.
And for Barcelona, they still haven't recovered, so I'm pessimistic about them being able to compete for the Champions League title.