It's written into the treaties that this will not be so. The goal of the EU is "ever closer union" and the people at the top of it routinely talk about a federal Europe in which the individual states disappear.
What exact treaty are you talking about, and what does it verbatim say? I've heard this so many times before, yet no one is able to link to concretely what they refer to. No texts I've seen has called for the dissolution of nation states in the EU or any of the other political structures.