I wish it were true Luis. That may be what's happening in Florida with the Cubans, but in the Southwest with the Mexicans, it is not inevitable.
Daily, I see immigrants from Mexico, young and old, and their US born children, that have been here for 10 or more years, and still can not speak English. The sad part is, when I ask them why they have not learned to speak English, the answer is always the same. I don't have to.
We have accommodated the Mexican immigrant so much in the southwest, that they no longer have to learn the language.
The European immigrants that come, learn the language just like you said. With in three generations, they don't speak their native tongue.