Recently Montenegrin President Yakov Milatovic declared a political goal to be a member state by 2028

https://www.bta.bg/en/news/balkans/691717-president-radev-bulgaria-supports-montenegro-s-european-integration

Of the states negotiating for membership, Montenegro has been going on the longest.

It is the only state which has met the interim benchmarks for negotiation.

https://www.consilium.europa.eu/en/press/press-releases/2024/06/26/sixteenth-meeting-of-the-accession-conference-with-montenegro-at-ministerial-level/

This market will resolve YES if Montenegro is a member state of the EU on 1st Jan 2028.

In the event of a name change, borders change, etc, this market will resolve depending on the EUs official stance.