It totally depends on the global adoption of cryptocurrencies.
More clearly there are two scenarios.
1) If community remains the same and bitcoin reaches $100K : Then except few top alts all altcoins market will crash badly.
2) If community grows along with the price and bitcoin reaches $100K : It will not going to effect altcoins market badly except crap coins.
It will definitely affect the entire market and never know if altcoins will follow so or numbers of altcoins will die. Having that $100k is pretty much high and giving the doubts that people/investors will look its potential anymore cause of its risk. Or they might change there mind instead of investing Bitcoins, they will go for altcoins.
I think that if Bitcoin reaches 100k, it is very favorable, from experience, I know that when bitcoin starts its Bullish Trend Stage, the altcoins will go down a lot, this is because they sell them fast and thus they do not miss the rise of bitcoin It is normal.
When the altcoins are rising, they go down, but if bitcoin continues to rise, the altcoins will start to rise too, because the trend is bullish and many who are with bitcoin will start to take their money in the altcoins, because they know that the altcoins will continue to rise, which, I think the altcoins will not stay on the road, especially the first of the top of CMC, since they have structures very similar to bitcoin and will not be left behind.
That's why I think that when Bitcoin becomes bullish, the market will be greener than ever, and will have a direct step to a new evolution in the whole market, just as it happened in 2017, when bitcoin was in a bullish trend, most of Altcoins went up and got their ATH, and they dropped the price just when bitcoin started to fall in price.