Particularly real or structural convergence is a process that takes time and continues after accession to the EU. Portugal may serve as an example: after membership, it took Portugal seven years to enter ERM I in 1992 and fully liberalise capital flows and another seven years to enter EMU.
In the early nineties, at the time of the Maastricht treaty, Portugal and Spain appeared to be at a higher level of structural convergence than the accession countries at the current stage. It seems unlikely that at the time of accession a sufficient level of structural or real convergence can be guaranteed in order to be able to commit to EMU.