It's a bit more complicated than this, because the treaties don't really have any mechanism for unilaterally expelling a member state and there is no precedent for doing so. The reality is there is no easy answer to what happens when a national constitution is incompatible with EU law.
Member states can, in theory, be suspended, though we've seen when it comes to Hungary and Poland that mechanism is quite hard to use (as it requires unanimity of all of the other member states) and it's considered the "nuclear option".
