that could happen but i don't think it will be anytime soon unless a major hack or something. however i do believe it could possibly lose dominance in the near future.
This is one of the impossible thing to phase out bitcoin because it is the strongest coin of this era and those who tried to harm it are attracted toward it because of its profit giving nature, and now the bitcoin is name of faith one possibility is there if there is no one in the world bitcoin can be phased out so keep your motives high, invest and enjoy.