No, another cryptocurrency (the word crypto is already used to mean something else) can gain steam while the price of BTC goes sideways or down, and eventually win. Just saying the statement "no matter what happens" is false.
Can is not the same as Will. 500M people could download the Lyft app tomorrow and stop using Uber, but they won't. I can't predict the future for BTC, no one can, but I'm skeptical of it being supplanted. It's got a huge lead in public awareness, and the public doesn't understand crypto currencies and isn't looking for new ones.