From the most recent issue of the International Journal of Lexicography
one can find highly interesting cases of the 'Eskimo hoax'
type in accounts of the history of Polish vocabulary, the one most often found being the statement that there are 30,000 'new words' (and one million technical terms) in Polish that appeared after 1945. This claim is not based on adequate empirical data. Piotr Wierzchon discusses the hoax on pages 178-183 of the book under review [Depozytorium leksykalne jezyka polskiego. Nowe fotomaterialy z lat 1901-2010.
Unfortunately I don't have access to the book being reviewed. Nor do I know Polish, so I couldn't read it even if I did. So that's all I can find out about this Polish vocabulary hoax. (Though it sounds more like an urban legend than a hoax.) Googling '30,000 new words in Polish since 1945' doesn't turn up anything helpful either.
However, a January 2013 article in The Independent
notes that Polish is now the second most widely spoken language in England and Wales, after English itself. And that this Polish-English contact is having a large influence on the Polish language, especially Polish business speak, which is adopting numerous English terms:
Polish translator Anna Lycett, 25, from Leeds said that English office terminology is being adopted. "Mostly English is incorporated into Polish in business speak, so terminology used in the office would be English rather than Polish: for example you would go to a 'briefing' rather than use the Polish word for it," she told the Huffington Post.
She added: "Marketing is often referred to as 'marketing' and you would also say 'IT' rather than the 'technologia informacyjna' or 'TI' either. People tend to use these English words whether they fully understand what they mean in English or not. PR is also Polonised so it is pronounced like the English 'PR' but spelt in Polish to reflect the pronunciation 'piar'.
Based on this, I would imagine that it must be true that there have been many new words added to Polish since 1945. But apparently not 30,000 new words (and 1 million technical terms).