If FLCL season 2 and 3 end up horrible
Just remember the original six episodes still exist and regardless of what happens in the new series it can't undo the awesomeness that is FLCL and how it has affected your life! just like with the Star Wars prequels and sequels, despite destroying your hopes and dreams, doing the old cast dirty, and ruining the canon, the original trilogy is still intact and will always be what you loved and got you into it to begin with.
(ignoring the special editions as well of course)
the original didn't do anything for me, other than confusion. So I don't think its anything particularly amazing like so many other people. I am interested in these two new seasons and will watch, but personally for me, the only way to go is up