Personally I'd not count on Bitcoin falling against anything else, unless a problem with Bitcoin itself causes it. Though that's not to say that anything can't help. Just like in all free markets, anything can happen...A new Bitcoin contender may already rising in the ranks though has not yet matured enough to be alongside or near it (one comes to mind), or, Bitcoin becomes insecure and another takes the crown...or maybe there will never be anything as economically sound, innovative or secure as Bitcoin (I share this with a big shift in the top 10 in the coming 5 years). The way that it grew and evolved is irreplaceable I would say.