soon. But once the world runs out of oil, the climate is decimated, and population comes crashing down because of restrictive immigration laws, there will be a sharp curve to the left and pro-EU that could lead to more interest in federation.

Or

This. Also, throw in the mix a backlash against nationalists abusing the cultural power void that might appear if both the US and the UK are collapsing - including the media industries -, the soft power of English declines, and instead of mass adoption of Mandarin in the stead of English we might try again Esperanto (which might not be the perfect universal language, but it could be perfect for Europeans).