I suppose that nobody thought that BTC could reach 17000 (somewhere even 20000) before the end of this year. I believe that it will raise up to 50k for sure, perhaps 100k. But it doesn't mean that any other alts are useless. I guess some of them could grow even faster than btc.
Yes bitcoin and altcoins can walk at the same way to make sure both are surviving.
Bitcoin go very high and altcoin look like drop in blood with red colour but if you see in usd comparison i think its not so much different.