Bitcoin, of course, can be overthrown by other crypto-currencies if it does not improve in time and eliminate its shortcomings. However, hardly ripple is now a direct competitor to bitcoin, and in the future, I think, too. Most likely, its rival in leadership will remain ethereum, although they are not direct competitors, because they perform various functions. Also competitors of bitcoin can be generally younger coins, which have not shown themselves now, because the crypto currency is developing very quickly.