Catalan just declared the independence, I hope La Liga allow Barcelona to stick with La Liga, there are many disadvantages if Barcelona decided to join another league if Barcelona join a French league or EPL they should start from the lowest league, and if Catalan make their own league, it's not competitive and they must wait a couple years to join UCL
No other league in European championships, will not invite Barcelona to play. Do you have any idea what this threatens, for example, the French League 1 from FIFA or UEFA ?! They will play in their own championship of Catalonia and make people laugh.