There is a good chance that coins with better specs and better foundation may take over from Bitcoin in popularity. I think BTC may always remain a solid investment, but growth wise, there are other coins to look out for that may be a better investment as the general public catches up on these.
there is no chance for any coins to defeat bitcoin. Because all of them are alternative coins.
Bitcoin is popular whole over the world but maybe some coin will popular on a particular place. But not in whole world.