I believe we'll go back to 2022 Bitcoin dominance by 2022.
The next halving should have put us past 6 figures, somewhere from $100,000 to $500,000 (to difficult to know where it will peak before the crash once we get past the 6 figure psychological barrier which is an huge accomplishment.. I predict tons of people getting rekt as they sell at $100,000 and open shorts expecting the price to crash right at $100,000)
By then the fact that most alts are scams should be obvious to even noobs and BTC will go back to the natural 80% balance as per pareto law distribution.
The alternative is there is a possibility we don't quite get past $100,000 and fall right before getting there, which would give us a a year or two of dipping before we actually get past $100,000 which will definitely crush altcoins.
The only problem with your logic is that it is illogical when comparing market share history. Ethereum has proven that other coins can substantially seize market share by being just as successful as bitcoin. This is what happens with technology. Microsoft didn't make windows. They stole it and made it the number one used OS all over the world. Who's to say some other coin won't do the same thing bitcoin has done but better?
Bitcoin is hugely important but its market share was also largely supplanted with ethereum market share with the ICO craze. Necessity is the mother of invention and ask most people in the crypto community what we need and it won't be bitcoin market share. What we need is other successful coins like ethereum to continue to be successful and to a large degree we are seeing this. The other thing we need is stability. bitcoin is a fine utility coin but better coins that will have assured stability will appeal more to mass adoption. This may not be to bitcoin purists liking but that doesn't really matter. A technology comes along like blockchain and it is the new jet engine of our times. It will open up parts of the world that were previously blocked. But bitcoin alone won't do this and the downward trend of BTC market share over the years is further proof of this.