This may be kneejerk, but I can only trust the evidence and circumstances apparent to me.
I believe that this is most likely the end for Barcelona's cycle. Barca bounced back from the post 2012 decline to win another treble, but I think this time our fall will be more permanent. It might sound like all doom and gloom but I'm basing this on one assumption:
The club will continue to be run in the same way and that there will be no major change in the approach to the sporting project.
If the above assumption is true, which I am 80-90% sure of, then it's only logical to assume that the club is destined for decline. After all, with the state of this squad/tactics there is a massive need for change to the sporting project from the top down.
The club sticking to their methodology means that Unzue is most likely to be the next manager, which would be a continuation of the glaring failures of the current project. The alternative, Valverde, does not bring much hope either as he is conservative and the rebuilding demands are likely above his abilities/intuition. I simply don't see him bringing any real change either. As far as transfers are concerned, I strongly expect us to not properly address the issues in defense or midfield. Iniesta is past it, Rakitic is struggling, and the rest are abysmal. Only Busquets would make it into an *ideal* version of next season's team. Our midfield is in total ruins, and what's the solution? Keeping Gomes? Buying Coutinho? Lol. Our midfield is shit and I would put money that it stays shit. If we switch back to 4-3-3, we need a RB: the only 'supposed' option is Bellerin who is trash. If we stay with 3-4-3 we need a CB because Mascherano is shit. Signings that could potentially 180 our situation (like Verratti) are simply not happening; if anything Verratti will be even more attracted to Juve after this thrashing is finalized over two legs. Signing Dybala/Dembele while the rest of our squad clearly suffers like this will fix nothing, and only waste career years for those players having come here hoping for success. Current key players like Messi/Pique/Busi are nearing their declining years as well, and they will no longer be able to hold up the team as they have. The transfer hurdles that Barca have to overcome to make this squad able to compete over the next few years with the likes of Bayern/Juve/RM are very high.
The only reliable way for Barca to rise up once more is for a serious diversion from the path that the club is currently taking, and there is NO ONE in a position of power who can/will induce this. With the current board, Robert won't be fired. With all of the (undeserved) power that Robert has, the new coach will be limited to Unzue/Valverde and the transfers will continue to be in the vain that we've seen. There simply is no force for change in the club at the moment, my optimism for the next few years is miniscule at best.