First of all, I don't really understand why we would need another midfielder next season. We have Xavi, Iniesta, Thiago. Song could also be played there like Keita was and Cesc should ONLY play in midfield (intstead of DM I mean). Another thing is, La Masia produces some fine players - especially midfielders. Sergio Roberto is coming through slowly, we also have Rafinha and Samper slowly making their way through.
IF we intend to buy a CM, it could probably only happen if Cesc or Song leaves. Than I would prefer Ilkay Gundogan to replace them. He can play more defensively if needed and has a set of skills very similar to Xavi. Isco is a good prospect, but both Thiago and Cesc are better players than him - I don't really see Isco as somebody 'controlling' the midfield, he is very direct.
I was thinking same thing early ,but the more I think about it looks different to me
Xavi is starting to decline tbh ,yes he is still putting amazing passing accuracy rate with his passing ,but let's be honest here ,he isn't his former self this season even if he still can have some gr8 games
I think it might be the time to decrease his games ,dare to say lose his starting spot too? Cesc has been inconsistent ,Thiago is good but do the management trust him for next year as a starter? I hope so but not sure the board have same opinion
Also Iniesta might still find himself shifting to LWF from time to time
Ilkay might be a good option to continue improving our midfield ,It isn't an urgent need for now in comparison to all other 3 lines(GK,Defense,attack) ,but I think this could emerge as a big problem next year and it might be good thing to avoid it b4 it happens
On other note ,there is also a lot of rumors of him joining Real Madrid
Edit : As for youngsters
Roberto isn't barca material ,he should be sold , he is good for mid table teams not FCB ,people are seriously overrating him ,Samper is 2 years away from being promoted , a lot can happen in those 2 years
Rafinha might be the only one that can be with first team ,but you can't count a lot on him ,Honestly I think Barca are overusing their youngsters at this point ,Unlike Deulofeu he is more of a long term project who should get into the team slowly in the next few years