This will not happen I think because bitcoin is the king of crypto and ripple is just an altcoins, bitcoin is already proven and people want to have it than ripple, even ripple can't beat ethereum in crypto market.
it doesnt need to defeat bitcoin and ethereum to become king. being extension of the king plus some exclusive power of own is not bad either.
Ripple goes against everything Bitcoin stands for. Bitcoin is a decentralized currency while Ripple is not. Bitcoin is mined by proof of work while ripple is not. Bitcoin is the people's coin while ripple is the banker's coin.
we need both centralize and decentralize coin to make it crypto work. at least at the moment. i believe both method will merge become something that transcend bitcoin and altcoin.