Nope, Alt's are here for awhile for sure.  You just need to be a bit smarter about what you are mining...and how you are trading. 

Alts are for day-trading, LTC/BTC are for long term investments. 

Think cryptos in general are going away?  Not anytime soon, check out this article - http://www.nbcnews.com/business/porn-basketball-taxes-bitcoin-hot-streak-2D11940201