Although there may be a vote in Catalunya for independence, it won’t be possible to achieve with the agreement of the Spanish government, whatever the catalans may think or wish. Even without thinking of civil unrest, apart from the french border spain could basically isolate catalunya from the rest of Spain, closing roads, rail, air transport.
If Spain did this (and I can think of quite a few reasons why it wouldn’t) then it would actually leave itself “isolated” from the rest of the world apart from the route to France via the Basque country. I can think of a few more reasons why Spain wouldn’t want that.
I disagree with you on this point chopera, lets not forget that the spanish government is the globally officially recognised representive of all spanish people (including catalans) and it was democratically elected. How different would a break away catalan state really be from basque separatists for example. Do you really thing the world would support or recognise an independent catalunya if it was declared null and void or illegal by the government?
I find that hard to believe, national governments would be storing up trouble for themselves in their own countries in setting such a precedent. I guess there are other similar examples of potential break away states/regions in many countries in the world.