The former communist countries of Central and South-Eastern Europe are now mostly NATO and EU members. The exceptions are the countries of the Western Balkans, which, at least declaratively, have a European perspective, with NATO as the probable entry check point (except for Serbia). The economic situation in the region is however less optimistic. The GDP per capita of the "most developed" Western Balkans state is still lower than the GDP of Bulgaria. Demographic challenges in some of the Western Balkans states are staggering (as well as in the Baltic States, Romania, Bulgaria, Hungary, and Croatia), with Albania, BosniaHerzegovina, Kosovo, and Serbia losing 12.4, 22.2, 13.0, and 9.1 percent of their population from the peak population year until the year 2018, respectively. With the possible accession to the EU, the emigration from all Western Balkans states would most likely increase; hence gradual or instant opening of the EU labour market has been the most significant factor influencing the demographic characteristics of post-communist EU members. The EU Strategy for the Western Balkans was revealed in February 2018. The Bulgarian presidency of the EU (the first half of 2018) has put the Western Balkans high on the priority list, and so has the Austrian presidency (the second half of 2018). How will the forthcoming enlargement envisioned by the European Commission improve regional development? How realistic is that the Western Balkans will be integrated into the EU by 2025 and what could be the major implications for these states? By studying statistical data and social processes, we compare the results of the EU membership for Croatia, Romania, and Bulgaria, the three most recent EU member states, and try to predict the most important developments in the Western Balkans states, that would likely occur after the accession to the EU.