Eh, I think it depends. If the Spanish government now takes over the Catalonian government and schedules new elections, and the anti⁻independence parties win by a reasonable margin, it may deflate the whole thing.
If there's actual major popular support for independence, then yeah, I don't see how the Spanish government can defuse that grenade without major concessions, which I don't see Rajoy accepting, so it could get very messy.
(Don't take my opinion very seriously, though; while I have close ties to Spain I don't have any particular knowledge about this situation)
If Catalonia somehow cedes from Spain/EC then there will probably be repercussions around Europe.
I was extremely surprised the other day to see a Welsh person who I'm acquainted with calling for civil war against the English. I sincerely hope there are not enough with such madness to make any thing viable in that respect, but the do seem to be substantial communities in other regions of the EC where things could kick off too.
If there's actual major popular support for independence, then yeah, I don't see how the Spanish government can defuse that grenade without major concessions, which I don't see Rajoy accepting, so it could get very messy.
(Don't take my opinion very seriously, though; while I have close ties to Spain I don't have any particular knowledge about this situation)