Bitcoins won't fail due to a bubble. Maybe not even a hack. They will fail for basically the same reason any fledgling currency of any new country fails: instability. And you're seeing it now -- a pizza that cost once 10k bitcoins now costs 1/15th of one. These are MASSIVE stability swings. There is no stability. The buying power of a bitcoin is, and as far as I can tell, will always be, subject to huge swings. Why? Because there is no mechanism by which supply can ever be calibrated to demand. There are a max of 21MM coins -- that's it, can't expand, ever. Bitcoins will always be a type of speculation / bet -- which is interesting, to be sure, but fails the test for a good digital currency because a fundamental tenant of a good currency, a desirable currency, is it has relatively stable buying power.
But it is fascinating to watch. Bitcoin 1.0 just fundamentally lacks any design considration for price stability, that coupled with an artificially set 21MM total bitcoins, and it is like instability is actually baked into the design.
Bitcoin 2.0 should have a mechanism to improve price stability -- this is no trivial task, however, and if there are any econ folks out there I'd love to hear any ideas on this point. Would require approx equaling supply and demand, but evening knowing when you've done this is tricky.