I don't think anybody should "rule" it, though it's probable that Germany would have the greatest power of all.
About the language, I also love my language, but I wouldn't be worried to lose it. Most young people (and in the west the old ones too) already speak English very well alongside their mother language, and yet the languages are not disappearing. Evolution of language and loaning new words is inevitable, anyway.
Also, I'm not sure where you are from, but look up National revivals / renaissances of various nations throughout Europe. For most Slavic nations, this happened in the 18th and 19th century, it's also happening now in Wales and somewhat in the Baltic states too, and I'm pretty sure many other nations will go through a revival in the future (native Americans, native Africans, etc when things get sorted out in these regions). It is possible to revive a language, shall it be necessary.
Of course Germany would have the greatest power and i don't want that.
I am, from Portugal, and Portuguese is one of the most beatiful languages in the world, it would be really sad to lose it.
About cultural homogenization i agree with you, Wikiy. You made a good point.
It's just a bit sad, after almost 1000 years of history if this would happen, all my grandchilds and their sons in a few decades would not know about Portugal and how we were small but fought for our country against, Spain, France, Roman Empire etc and we managed to secure our little corner and keep it to ourselves, free from others.
Oh, well, i guess it's for the best. Some generations would be sad but the others after would benefit from a united Europe.