I don't think that alts will be drought even after BTC reaches the gazillion amount. In fact investors might even consider investing in alts after they felt the success they got from BTC.
Both of these parties do not depend to each other. They have their own goals in terms of utilization and price (ETH, XRP, etc vs Bitcoin).
If you're trying to scare investors, right now. Sorry it is a bad attempt, and no one would twitch their emotions from that.
I think if Bitcoin will touch the $100k, it will be scary for the team of each altcoins, imagine people will trust more Bitcoin as they have seen the great potential of it, so the scariest thing that will happen for this is that they will give up all their coins and will just hold Bitcoin in long term. Anyway, touching $100k is far from the reality now, it may take a lot of years before it will happen.