Amid much fanfare, 10 candidate countries will toast the end of lengthy accession talks at a European Union summit next month that should pave the way for a historic unification of the continent.
As Poles, Hungarians and Czechs celebrate in Copenhagen, many nations still left outside the EU fold can be forgiven for fearing a new division of Europe into haves and have-nots.
Russians, Ukrainians, Albanians and Serbs will need visas to enter the new member states. And they can only watch enviously as the new members tap generous EU funds to help struggling farmers, clean up their environment and rebuild crumbling roads.
In Brussels, policy-makers insist that eastern enlargement will benefit the whole continent, but they are also increasingly sensitive to the problems a redrawn map of Europe will pose.
"It would be destabilising if we were to allow a gulf in living standards and standards of government to open up between the (enlarged) European Union and its eastern neighbours," said EU External Affairs Commissioner Chris Patten recently.
The 10 states hoping to close talks in December and to join the EU in 2004 are Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia.
Patten, along with EU foreign policy chief Javier Solana, has urged the bloc to think carefully about how to handle the "new neighbours" - a term embracing the former Soviet Union, the ex-Yugoslav republics, Albania and Mediterranean rim countries.
They have proposed more economic aid, a freeing up of trade, more political dialogue and practical cooperation in areas such as border security and tackling illegal immigration.
"The pace and scope of this process will have to be flexible - there can be no one-size-fits-all approach," Patten and Solana said in a joint letter to EU foreign ministers.
The enlarged EU's neighbours are certainly a mixed bunch. First, there are the so-called Western Balkans, a clutch of small, impoverished countries still suffering the after-effects of the bloody implosion of Yugoslavia during the 1990s. But their long-term future in the EU, at least, appears secure.
"The Balkans, whatever the timetable is, are destined to become part of the European family. They are a region we have to look after," said European Commission President Romano Prodi.
The accession of the two eastern Balkan countries, Bulgaria and Romania, possibly as early as 2007, should help galvanise reform efforts in Serbia and Montenegro, Macedonia, Bosnia, Croatia and Albania, EU diplomats said.
Indeed, Croatia and Macedonia have already negotiated a so-called Stabilisation and Association Agreement - the first step on the long road to eventual EU membership.
A second grouping of countries, on the southern and eastern Mediterranean rim, would also probably like to join the EU but are excluded on geographical grounds and, in any case, mostly fail the EU's strict standards on democracy and human rights.
Morocco once applied to join but was swiftly rejected. The one exception is Turkey. It became an official candidate in 1999, despite the reservations of many who considered it too big, unwieldy and Muslim to join what some would prefer to keep a "Christian club".
Following an election last Sunday (November 3) that swept a new and seemingly moderate pro-EU party - the AKP - into power, Ankara hopes to win a date in Copenhagen to start accession talks, long delayed due to worries over its human rights record.
Diplomats say Turkey should win at least a "date for a date" - that is, a pledge to review its progress at a later stage.
Beyond Turkey lie the small and still unstable ex-Soviet republics of the Caucasus - Georgia, Armenia and Azerbaijan - which would also like to join the EU one day.
"If Georgia fulfils the EU's political and economic criteria in, say, 20 years, why should it not be allowed to join?" said Heather Grabbe of the Centre for European Reform, a London-based think-tank.
"Europe is about values, it is a frame of mind, not just geography," she told Reuters.
But the immediate challenge after the current enlargement looks set to come from the countries bordering central Europe.
Ukraine, in particular, has been trying to forge closer economic and political ties with the EU, though President Leonid Kuchma, dogged by allegations of corruption and misrule, is mistrusted in many European capitals. (Reuters)
Here, new member states such as Poland will have a key bridging role to play, EU diplomats said.
Polish President Aleksander Kwasniewski recently hosted a meeting of top EU and Ukrainian officials.
"A country like Poland knows from its own experience how much international organisations and institutions can help promote the transition to democracy and the free market," said a diplomat. "It can share that experience with its neighbours."
But not all the new neighbours seem willing to learn. "With Belarus we presently have virtually no formal relations," Patten and Solana acknowledged in their letter.
Under the authoritarian rule of President Alexander Lukashenko, Belarus has shunned European integration.
And tiny Moldova? "Europe's poorest country is in a state of crisis which could render any long-term strategy superfluous," said Solana and Patten. Relations with Russia, however, look much more promising.
On November 11, President Vladimir Putin will travel to Brussels for a summit which the EU hopes will seal an agreement on Russia's Baltic enclave of Kaliningrad, a flashpoint in relations between Moscow and the Union for more than a year.
Kaliningrad will be surrounded by EU territory once its neighbours Poland and Lithuania join the bloc, probably in 2004.
EU leaders have endorsed a plan that would require citizens of the enclave to have a visa to travel across Lithuanian territory to Russia proper.
Moscow has long argued that its citizens should not require a visa to move from one part of their country to another, but it now looks set to accept the plan because the EU has agreed to a feasibility study for a visa-free, high-speed rail link between Kaliningrad and Russia proper in the longer term.
A deal on Kaliningrad would remove a major irritant in EU-Russia relations and allow the two sides to focus on economic cooperation, especially in the domain of energy.
But few in Brussels see Russia, a vast country spanning 11 time zones, ever joining the bloc.
In a recent interview for the Italian newspaper La Stampa, Prodi went further in setting limits to EU expansion.
"As far as Russia, Ukraine, Moldova and countries of the southern Mediterranean are concerned, including Israel, you can link together many things - but not institutions," he said.
In other words, yes to closer economic and political cooperation, no to full-fledged membership.