This is not at all likely. Admittedly East Germany is an extreme example, of a country lacking a solid national existence populated almost entirely by people who would be eligible for citizenship in a prosperous Western country, but almost every territory and population in the Soviet bloc had at least some history of emigration. In some countries this tradition was stronger than in others--Poland had a history of large-scale emigration lacking in the Czech lands--but it existed everywhere. Even the wealthiest lands in the Soviet bloc were often poorer than their neighbours in western Europe, even before Communism. Later, this gap yawned.
This emigration would be huge. In Croatia from the 1960s on, for instance, almost a half-million people emigrated as gastarbeitar to various points in central Europe, out of a republican population of four million. Croatia's diaspora was a product of Yugoslavia's liberalization and opening to the west, as a way to relieve domestic unemployment and to acquire money that could be sent back home to spur domestic consumption. In the context of the 1960s, where roaring economic growth across most of western Europe created labour shortages that could be filled only by migrant labour, if Soviet bloc countries adopted Yugoslav-style policies I can imagine huge numbers of migrants being accepted. A Poland that had traditionally been a major source of migrants for Germany and France, even during the Cold War OTL, might resume this role. Who knows?
For relatively Yugoslavia-style permeable borders to be possible in the Soviet bloc, you will need to radically alter world history. At the very least, these countries and this bloc will need to be at least as friendly with western Europe as Yugoslavia. This means that the Cold War will not occur, or at the very least it will be hugely changed.