And with Brexit, the biggest obstacle to that has been removed - the UK never wanted to be part of a Federal EU (because we always considered ourselves part of the British Empire/Commonwealth). There are other EU countries who aren't wildly enthusiastic about a Federal EU too, but it was always the UK being the most loudly opposed to it.
Just look at what happens whenever some EU treaty needs ratifying by national referendum.
that never stopped it before, just look at the "Constitution for Europe"
rejected by the French and Dutch electorates
it was then rejigged slightly and then pushed through as the Treaty of Lisbon (without pesky referendums)
As a result, the EU agreed a set of guarantees [1] that the Lisbon treaty would not be used to do either of these things (to Ireland specifically), and only then did it pass in Ireland.
An EU army has more widespread opposition these days, so hasn't been raised since. Minimum corporate tax rates did not pass through the EU, though this year the US led an effort that is going to result in them globally via other avenues.
[1]: https://www.iiea.com/images/uploads/resources/230535195500_L...
this is false. very few european countries want a federal, unified state.
so nothing of meaning will happen until a lot of things change.