I don't think you can make a case for bitcoin destroying altcoins when a lot of them occupy completely different niche markets than BTC. BTC is only a currency coin, many altcoins aren't even competing against it, so how could they be destroyed/made irrelevant by it. Doesn't make any sense.
if you take into account Bitcoin or Bitcoin cash And also such as Bitcoin Gold, then any of these coins or similar other counterparts do not make sense at all. I think that it is much more complicated and more important in the world of crypto-currencies are those coins that provide real projects.
That's why escalating and scanning is properly do by the people who wish to invest on the alts since by looking on trend coins is not really good since anytime they might gonna dump badly enough and that could hurt us. And selecting good coins is really must for us since if we choose those coins who have existing project then we can have a little relief since they will not surely run off since they are earning success on this alt business.