Hm, let's see...

1. A (print) article referencing a (French) study titled "The decline of the Alsatian dialect" or something,
   
2. a (German) documentary I saw,
   
3. an article by an Alsatian I read a few months ago on the web,
   
4. my own admittedly very limited experience of not having heard a single German(ic) word when I was in Strasbourg for one day.

3. I do'nt see how it is suppressed.

Sorry, maybe not the best word I chose. I didn't mean suppression by force, I meant being eclipsed by the presence and use of the others. What you mention that many people learn Hochdeutsch rather than Alsatian is part of this (and parallels what happened and happens to some German dialects in Germany proper, BTW).

_{*Lunatic*, n.
One whose delusions are out of fashion.}