My opinion is that in time Bitcoin market share will keep reducing, as many other coins and tokens and platforms will keep surging.
In the long term, the blockchain technology is very disruptive. Bitcoin will more likely compete with Gold, Ethereum will provide a backbone for many uses.
So I am not really sure a collapse is incoming, it depends if a real bubble will quickly form.
I think it is the other way around many of the projects that currently exist will disappear in the future and when that happens then all of that money going to those alts is going to return to bitcoin so if anything it is likely bitcoin recovers some of the market share it has lost to other coins, it is not something that will happen in the next months but it could happen in the next 10 years.