Xavi is too loyal to be Barcelona coach and because of that, I think it was the right decision for Xavi to resign. Because anyway, the financial crisis that Barcelona is going through is really having a bad impact on the management of the team and also the performance of the team. So yes, although there will be a transfer window that will open later but still, it is difficult for Barcelona to be able to build a team with great players in the upcoming transfer window. So yes, even if Xavi stays at Barcelona but if Barcelona financial situation is still bad then of course, it is difficult for Xavi to improve the quality of Barcelona and it will never be easy to make Barcelona strong again in the title race.
Xavi Hernandez become most loyal manager for Barcelona and not give huge pressure for management must signing top players, Xavi can adapt well with current financial faced by Barcelona and he was success by winning La Liga tittle although with current financial condition facing. I don't think any new manager will adapt well how bad financial condition from Barcelona and likely seems not comfortable every windowt transfer opening Barcelona always difficult for signing top players.
But Xavi Hernandez journey with Barcelona have been over for this season, he leaves Barcelona for next season after bad respond from management and less respect what achievement so far giving by Xavi.