Of course it will fly - becuae the tired old 747 airframe can not be stretched out forever. Ok - it is a big projest with lots of bits and pieces made by lots of different companies and may end up a bit late because of any number of reasons. However, ground breaking projects are almost always hit by problems at some stage.
The design is well under way, the manufacturers want to build it and we will have 40 years to get our money back (look how long the B747 has been around) so we can afford to take the long-term view.
Of course the American industry would like it to fail A) because Boeing aren't building it b) becuaes the Europeans are building it and c) because Boeing aren't building it!!! Look at the green eyes of envy that followed Concorde as it made it's technologically brillaint but commercially flawed way into service. We are a lot better at this "co-operation" stuff these days, even if it means working WITH the French.
It will fly, it will sell and it will make money in the long run. Even if the A380 does not return a profit it will roll into A340/330/320 sales because of fleet commonality.