trend is unstoppable that euro will replace us dollar as no one will trust us dollar in the long term anymore
once they have crushed and whole world starts thinking in euro and potentially yuan.
To have a situation like you dream, the Chinese government has the potential to overthrow the US dollar as the global currency because they hold trillions of dollars worth of treasury bonds and only a mad man will initiate that sell off, basically it is a highly unlikely situation in the near future, that being said Euro is not the only reserve currency

. Not sure what Yuan is but if you are talking about Yen it is the third most used reserve currency.