I'm a linguist. (Edit: Even though that is true, my specialization is in semantics and neurolinguistics and I'm not an expert on either language history or change. I have taken courses on these topics and have discussed them with people who are experts, but I don't want to give the impression that I'm claiming more authority here than I have.)
What ClintMemo is proposing is highly unlikely. Syntax is tied in many ways to the lexicon - they can't change independently. For one, not all languages express the same concepts in the same way. Take the word "hungry". In English, this is an adjective. I can say "I am hungry". In other languages, the same concept would have to be expressed with a noun ("I have hunger", as in French), and I believe there are languages that express this notion with a verb ("I hunger"), though I don't remember which. It would be difficult to borrow these words from one language to another without changing the syntax to match. And this is just one of many, many examples.
More generally, people speak of language borrowings and change as if they are recent things. They are not. Languages have always changed and evolved over time - and it used to be a lot faster. Latin split up and became languages as different as early Italian, French, and Romanian in only several centuries. The Normans invaded England and turned Old English, a pure Germanic language, into the hybrid language that we speak today, with a lexicon that's about half Germanic, half Romance, and a syntax that's unlike any other European language. Then print came, and widespread education, and the process slowed down - once the written word became popular and massively accessible, the changes became more noticable. The 19th century gave rise to nationalism, and that led to a move to homogenize the languages spoke in the newly emerging countries. Languages became codified, but still they changed - read a 19th century novel and compare it to today's speech.
What has changed again, in the last quarter of the 20th century, is that mass media, and the internet, have changed the boundaries of language contact. Once, contact with foreign languages was limited to a relatively small sector of the population. Now, it's becoming easier and easier to be exposed to foreign languages, regardless of financial standing, education, or occupation. The effects of this are just starting to be understood, but they're neither as dramatic or unique as some of the above posts make it sound. Rather, it is the continuation of a process that has been going on throughout the life of the human race - languages have never been static, and never will be, despite the efforts of language codifiers. It is true that the number of languages in the world is on a rapid decline - but this is mostly because the number of societies is decreasing - the languages the world is losing are those spoken by tribes in South America, Africa, and Australia, which are becoming absorbed into larger societies, or wiped out by war and disease. As for the rest, more and more people in the Western world are becoming multi-lingual, speaking several languages, but this can have a lot of outcomes, merger of the languages being a highly unlikely one.
